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George Thomas - One of the best experts on this subject based on the ideXlab platform.

  • Abstract 2024: c-Myc driven B cell lymphomas: role of the RPL5/RPL11/5S rRNA-MDM2 inhibitory complex (L5/L11/5S-MIC)
    Molecular and Cellular Biology, 2015
    Co-Authors: Suresh Peddigari, Carol A. Mercer, Sara C. Kozma, George Thomas
    Abstract:

    We recently demonstrated that as a consequence of impaired ribosome biogenesis, the L5/L11/5S pre-ribosomal complex is redirected to inhibit Mdm2, leading to p53 stabilization (Donati et al., 2013). In seminal studies, Eμ-Myc mice were crossed into a hypomorphic ribosomal protein (RP) L24 mutant background, which brought global translation rates to normal and extended their disease-free survival, independent of p53 (Barna et. al. 2008). However, when this mouse model harbors a single point mutation of Mdm2, which cannot bind the L5/L11/5S-MIC, mice succumb to lymphomagenesis much more rapidly than wild type Mdm2 mice (Macias et al, 2010). Moreover, inhibition of Pol I, which selectively transcribes rRNA genes, suppresses Myc driven tumors, potentially through the same L5/L11/5S-MIC (Bywater, et al, 2012). To address the role of the L5/L11/5S-MIC versus that of global translation in the Eμ-Myc B cell lymphocytes, we partially depleted mRNAs for RPL11, which in other cell types has no effect on p53 levels, or RPL7a, which is known to induce p53 stabilization in a RPL11 dependent manner. We generated stable cell lines of inducible shRNAs against RPL11 or RPL7a using a tetracycline (Tet)-regulated miR30-shRNA system, TRMPVIR retroviral vector. By titrating doxycycline, we achieved ∼50% reduction of RPL11 or RPL7a transcript levels, with Renilla shRNA (Ren) as a control. A 50% depletion of RPL11 or RPL7a mRNAs led to an equal reduction in protein synthesis and ribosome biogenesis, however, RPL11 depletion did not alter p53 levels, whereas RPL7a mRNA depletion induced p53 stabilization and Caspase-3 dependent apoptosis. RPL7A or RPL11 depletion reduced cell proliferation to half that of control cells, with more cell death observed in RPL7a depleted cells versus RPL11 depleted cells. Treatment of RPL7a depleted cells with the caspase inhibitor ZVAD, or depletion of RPL7a in a p53 negative background suppressed cell death. Expression levels of the anti-apoptotic protein Mcl-1 were elevated in Eμ-Myc cells and unchanged in RPL11 depleted cells, but reduced in RPL7a depleted cells in a p53-dependent manner. This suggests that in RPL7a depleted cells, p53 regulates Mcl-1 levels to promote cell death and tumor suppression. Finally, immunoprecipitation of Mdm2 revealed the presence of L5/L11/5S-MIC in RPL7a depleted cells, but not in RPL11 depleted cells. Although p53 was not induced in RPL11 depleted cells, reduction of RPL11 to ∼95% led to acute cell death in both p53-/- and p53 +/+ Eμ-Myc cells, likely due to the inhibition of global translation. These findings demonstrate a differential abrogation of ribosome biogenesis by partial depletion of two essential RPs, which assemble at a very similar stage in 60S ribosome. For RPL7a, it led to L5/L11/5S-MIC induced p53 mediated cell death, and this was not the case for RPL11 as it is an essential component of the complex. Citation Format: Suresh Peddigari, Carol Mercer, Sara Kozma, George Thomas. c-Myc driven B cell lymphomas: role of the RPL5/RPL11/5S rRNA-MDM2 inhibitory complex (L5/L11/5S-MIC). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2024. doi:10.1158/1538-7445.AM2015-2024

  • abstract 2024 c myc driven b cell lymphomas role of the rpl5 rpl11 5s rrna mdm2 inhibitory complex l5 l11 5s mic
    Cancer Research, 2015
    Co-Authors: Suresh Peddigari, Carol A. Mercer, Sara C. Kozma, George Thomas
    Abstract:

    We recently demonstrated that as a consequence of impaired ribosome biogenesis, the L5/L11/5S pre-ribosomal complex is redirected to inhibit Mdm2, leading to p53 stabilization (Donati et al., 2013). In seminal studies, Eμ-Myc mice were crossed into a hypomorphic ribosomal protein (RP) L24 mutant background, which brought global translation rates to normal and extended their disease-free survival, independent of p53 (Barna et. al. 2008). However, when this mouse model harbors a single point mutation of Mdm2, which cannot bind the L5/L11/5S-MIC, mice succumb to lymphomagenesis much more rapidly than wild type Mdm2 mice (Macias et al, 2010). Moreover, inhibition of Pol I, which selectively transcribes rRNA genes, suppresses Myc driven tumors, potentially through the same L5/L11/5S-MIC (Bywater, et al, 2012). To address the role of the L5/L11/5S-MIC versus that of global translation in the Eμ-Myc B cell lymphocytes, we partially depleted mRNAs for RPL11, which in other cell types has no effect on p53 levels, or RPL7a, which is known to induce p53 stabilization in a RPL11 dependent manner. We generated stable cell lines of inducible shRNAs against RPL11 or RPL7a using a tetracycline (Tet)-regulated miR30-shRNA system, TRMPVIR retroviral vector. By titrating doxycycline, we achieved ∼50% reduction of RPL11 or RPL7a transcript levels, with Renilla shRNA (Ren) as a control. A 50% depletion of RPL11 or RPL7a mRNAs led to an equal reduction in protein synthesis and ribosome biogenesis, however, RPL11 depletion did not alter p53 levels, whereas RPL7a mRNA depletion induced p53 stabilization and Caspase-3 dependent apoptosis. RPL7A or RPL11 depletion reduced cell proliferation to half that of control cells, with more cell death observed in RPL7a depleted cells versus RPL11 depleted cells. Treatment of RPL7a depleted cells with the caspase inhibitor ZVAD, or depletion of RPL7a in a p53 negative background suppressed cell death. Expression levels of the anti-apoptotic protein Mcl-1 were elevated in Eμ-Myc cells and unchanged in RPL11 depleted cells, but reduced in RPL7a depleted cells in a p53-dependent manner. This suggests that in RPL7a depleted cells, p53 regulates Mcl-1 levels to promote cell death and tumor suppression. Finally, immunoprecipitation of Mdm2 revealed the presence of L5/L11/5S-MIC in RPL7a depleted cells, but not in RPL11 depleted cells. Although p53 was not induced in RPL11 depleted cells, reduction of RPL11 to ∼95% led to acute cell death in both p53-/- and p53 +/+ Eμ-Myc cells, likely due to the inhibition of global translation. These findings demonstrate a differential abrogation of ribosome biogenesis by partial depletion of two essential RPs, which assemble at a very similar stage in 60S ribosome. For RPL7a, it led to L5/L11/5S-MIC induced p53 mediated cell death, and this was not the case for RPL11 as it is an essential component of the complex. Citation Format: Suresh Peddigari, Carol Mercer, Sara Kozma, George Thomas. c-Myc driven B cell lymphomas: role of the RPL5/RPL11/5S rRNA-MDM2 inhibitory complex (L5/L11/5S-MIC). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2024. doi:10.1158/1538-7445.AM2015-2024

Suresh Peddigari - One of the best experts on this subject based on the ideXlab platform.

  • Abstract 2024: c-Myc driven B cell lymphomas: role of the RPL5/RPL11/5S rRNA-MDM2 inhibitory complex (L5/L11/5S-MIC)
    Molecular and Cellular Biology, 2015
    Co-Authors: Suresh Peddigari, Carol A. Mercer, Sara C. Kozma, George Thomas
    Abstract:

    We recently demonstrated that as a consequence of impaired ribosome biogenesis, the L5/L11/5S pre-ribosomal complex is redirected to inhibit Mdm2, leading to p53 stabilization (Donati et al., 2013). In seminal studies, Eμ-Myc mice were crossed into a hypomorphic ribosomal protein (RP) L24 mutant background, which brought global translation rates to normal and extended their disease-free survival, independent of p53 (Barna et. al. 2008). However, when this mouse model harbors a single point mutation of Mdm2, which cannot bind the L5/L11/5S-MIC, mice succumb to lymphomagenesis much more rapidly than wild type Mdm2 mice (Macias et al, 2010). Moreover, inhibition of Pol I, which selectively transcribes rRNA genes, suppresses Myc driven tumors, potentially through the same L5/L11/5S-MIC (Bywater, et al, 2012). To address the role of the L5/L11/5S-MIC versus that of global translation in the Eμ-Myc B cell lymphocytes, we partially depleted mRNAs for RPL11, which in other cell types has no effect on p53 levels, or RPL7a, which is known to induce p53 stabilization in a RPL11 dependent manner. We generated stable cell lines of inducible shRNAs against RPL11 or RPL7a using a tetracycline (Tet)-regulated miR30-shRNA system, TRMPVIR retroviral vector. By titrating doxycycline, we achieved ∼50% reduction of RPL11 or RPL7a transcript levels, with Renilla shRNA (Ren) as a control. A 50% depletion of RPL11 or RPL7a mRNAs led to an equal reduction in protein synthesis and ribosome biogenesis, however, RPL11 depletion did not alter p53 levels, whereas RPL7a mRNA depletion induced p53 stabilization and Caspase-3 dependent apoptosis. RPL7A or RPL11 depletion reduced cell proliferation to half that of control cells, with more cell death observed in RPL7a depleted cells versus RPL11 depleted cells. Treatment of RPL7a depleted cells with the caspase inhibitor ZVAD, or depletion of RPL7a in a p53 negative background suppressed cell death. Expression levels of the anti-apoptotic protein Mcl-1 were elevated in Eμ-Myc cells and unchanged in RPL11 depleted cells, but reduced in RPL7a depleted cells in a p53-dependent manner. This suggests that in RPL7a depleted cells, p53 regulates Mcl-1 levels to promote cell death and tumor suppression. Finally, immunoprecipitation of Mdm2 revealed the presence of L5/L11/5S-MIC in RPL7a depleted cells, but not in RPL11 depleted cells. Although p53 was not induced in RPL11 depleted cells, reduction of RPL11 to ∼95% led to acute cell death in both p53-/- and p53 +/+ Eμ-Myc cells, likely due to the inhibition of global translation. These findings demonstrate a differential abrogation of ribosome biogenesis by partial depletion of two essential RPs, which assemble at a very similar stage in 60S ribosome. For RPL7a, it led to L5/L11/5S-MIC induced p53 mediated cell death, and this was not the case for RPL11 as it is an essential component of the complex. Citation Format: Suresh Peddigari, Carol Mercer, Sara Kozma, George Thomas. c-Myc driven B cell lymphomas: role of the RPL5/RPL11/5S rRNA-MDM2 inhibitory complex (L5/L11/5S-MIC). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2024. doi:10.1158/1538-7445.AM2015-2024

  • abstract 2024 c myc driven b cell lymphomas role of the rpl5 rpl11 5s rrna mdm2 inhibitory complex l5 l11 5s mic
    Cancer Research, 2015
    Co-Authors: Suresh Peddigari, Carol A. Mercer, Sara C. Kozma, George Thomas
    Abstract:

    We recently demonstrated that as a consequence of impaired ribosome biogenesis, the L5/L11/5S pre-ribosomal complex is redirected to inhibit Mdm2, leading to p53 stabilization (Donati et al., 2013). In seminal studies, Eμ-Myc mice were crossed into a hypomorphic ribosomal protein (RP) L24 mutant background, which brought global translation rates to normal and extended their disease-free survival, independent of p53 (Barna et. al. 2008). However, when this mouse model harbors a single point mutation of Mdm2, which cannot bind the L5/L11/5S-MIC, mice succumb to lymphomagenesis much more rapidly than wild type Mdm2 mice (Macias et al, 2010). Moreover, inhibition of Pol I, which selectively transcribes rRNA genes, suppresses Myc driven tumors, potentially through the same L5/L11/5S-MIC (Bywater, et al, 2012). To address the role of the L5/L11/5S-MIC versus that of global translation in the Eμ-Myc B cell lymphocytes, we partially depleted mRNAs for RPL11, which in other cell types has no effect on p53 levels, or RPL7a, which is known to induce p53 stabilization in a RPL11 dependent manner. We generated stable cell lines of inducible shRNAs against RPL11 or RPL7a using a tetracycline (Tet)-regulated miR30-shRNA system, TRMPVIR retroviral vector. By titrating doxycycline, we achieved ∼50% reduction of RPL11 or RPL7a transcript levels, with Renilla shRNA (Ren) as a control. A 50% depletion of RPL11 or RPL7a mRNAs led to an equal reduction in protein synthesis and ribosome biogenesis, however, RPL11 depletion did not alter p53 levels, whereas RPL7a mRNA depletion induced p53 stabilization and Caspase-3 dependent apoptosis. RPL7A or RPL11 depletion reduced cell proliferation to half that of control cells, with more cell death observed in RPL7a depleted cells versus RPL11 depleted cells. Treatment of RPL7a depleted cells with the caspase inhibitor ZVAD, or depletion of RPL7a in a p53 negative background suppressed cell death. Expression levels of the anti-apoptotic protein Mcl-1 were elevated in Eμ-Myc cells and unchanged in RPL11 depleted cells, but reduced in RPL7a depleted cells in a p53-dependent manner. This suggests that in RPL7a depleted cells, p53 regulates Mcl-1 levels to promote cell death and tumor suppression. Finally, immunoprecipitation of Mdm2 revealed the presence of L5/L11/5S-MIC in RPL7a depleted cells, but not in RPL11 depleted cells. Although p53 was not induced in RPL11 depleted cells, reduction of RPL11 to ∼95% led to acute cell death in both p53-/- and p53 +/+ Eμ-Myc cells, likely due to the inhibition of global translation. These findings demonstrate a differential abrogation of ribosome biogenesis by partial depletion of two essential RPs, which assemble at a very similar stage in 60S ribosome. For RPL7a, it led to L5/L11/5S-MIC induced p53 mediated cell death, and this was not the case for RPL11 as it is an essential component of the complex. Citation Format: Suresh Peddigari, Carol Mercer, Sara Kozma, George Thomas. c-Myc driven B cell lymphomas: role of the RPL5/RPL11/5S rRNA-MDM2 inhibitory complex (L5/L11/5S-MIC). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2024. doi:10.1158/1538-7445.AM2015-2024

Carol A. Mercer - One of the best experts on this subject based on the ideXlab platform.

  • Abstract 2024: c-Myc driven B cell lymphomas: role of the RPL5/RPL11/5S rRNA-MDM2 inhibitory complex (L5/L11/5S-MIC)
    Molecular and Cellular Biology, 2015
    Co-Authors: Suresh Peddigari, Carol A. Mercer, Sara C. Kozma, George Thomas
    Abstract:

    We recently demonstrated that as a consequence of impaired ribosome biogenesis, the L5/L11/5S pre-ribosomal complex is redirected to inhibit Mdm2, leading to p53 stabilization (Donati et al., 2013). In seminal studies, Eμ-Myc mice were crossed into a hypomorphic ribosomal protein (RP) L24 mutant background, which brought global translation rates to normal and extended their disease-free survival, independent of p53 (Barna et. al. 2008). However, when this mouse model harbors a single point mutation of Mdm2, which cannot bind the L5/L11/5S-MIC, mice succumb to lymphomagenesis much more rapidly than wild type Mdm2 mice (Macias et al, 2010). Moreover, inhibition of Pol I, which selectively transcribes rRNA genes, suppresses Myc driven tumors, potentially through the same L5/L11/5S-MIC (Bywater, et al, 2012). To address the role of the L5/L11/5S-MIC versus that of global translation in the Eμ-Myc B cell lymphocytes, we partially depleted mRNAs for RPL11, which in other cell types has no effect on p53 levels, or RPL7a, which is known to induce p53 stabilization in a RPL11 dependent manner. We generated stable cell lines of inducible shRNAs against RPL11 or RPL7a using a tetracycline (Tet)-regulated miR30-shRNA system, TRMPVIR retroviral vector. By titrating doxycycline, we achieved ∼50% reduction of RPL11 or RPL7a transcript levels, with Renilla shRNA (Ren) as a control. A 50% depletion of RPL11 or RPL7a mRNAs led to an equal reduction in protein synthesis and ribosome biogenesis, however, RPL11 depletion did not alter p53 levels, whereas RPL7a mRNA depletion induced p53 stabilization and Caspase-3 dependent apoptosis. RPL7A or RPL11 depletion reduced cell proliferation to half that of control cells, with more cell death observed in RPL7a depleted cells versus RPL11 depleted cells. Treatment of RPL7a depleted cells with the caspase inhibitor ZVAD, or depletion of RPL7a in a p53 negative background suppressed cell death. Expression levels of the anti-apoptotic protein Mcl-1 were elevated in Eμ-Myc cells and unchanged in RPL11 depleted cells, but reduced in RPL7a depleted cells in a p53-dependent manner. This suggests that in RPL7a depleted cells, p53 regulates Mcl-1 levels to promote cell death and tumor suppression. Finally, immunoprecipitation of Mdm2 revealed the presence of L5/L11/5S-MIC in RPL7a depleted cells, but not in RPL11 depleted cells. Although p53 was not induced in RPL11 depleted cells, reduction of RPL11 to ∼95% led to acute cell death in both p53-/- and p53 +/+ Eμ-Myc cells, likely due to the inhibition of global translation. These findings demonstrate a differential abrogation of ribosome biogenesis by partial depletion of two essential RPs, which assemble at a very similar stage in 60S ribosome. For RPL7a, it led to L5/L11/5S-MIC induced p53 mediated cell death, and this was not the case for RPL11 as it is an essential component of the complex. Citation Format: Suresh Peddigari, Carol Mercer, Sara Kozma, George Thomas. c-Myc driven B cell lymphomas: role of the RPL5/RPL11/5S rRNA-MDM2 inhibitory complex (L5/L11/5S-MIC). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2024. doi:10.1158/1538-7445.AM2015-2024

  • abstract 2024 c myc driven b cell lymphomas role of the rpl5 rpl11 5s rrna mdm2 inhibitory complex l5 l11 5s mic
    Cancer Research, 2015
    Co-Authors: Suresh Peddigari, Carol A. Mercer, Sara C. Kozma, George Thomas
    Abstract:

    We recently demonstrated that as a consequence of impaired ribosome biogenesis, the L5/L11/5S pre-ribosomal complex is redirected to inhibit Mdm2, leading to p53 stabilization (Donati et al., 2013). In seminal studies, Eμ-Myc mice were crossed into a hypomorphic ribosomal protein (RP) L24 mutant background, which brought global translation rates to normal and extended their disease-free survival, independent of p53 (Barna et. al. 2008). However, when this mouse model harbors a single point mutation of Mdm2, which cannot bind the L5/L11/5S-MIC, mice succumb to lymphomagenesis much more rapidly than wild type Mdm2 mice (Macias et al, 2010). Moreover, inhibition of Pol I, which selectively transcribes rRNA genes, suppresses Myc driven tumors, potentially through the same L5/L11/5S-MIC (Bywater, et al, 2012). To address the role of the L5/L11/5S-MIC versus that of global translation in the Eμ-Myc B cell lymphocytes, we partially depleted mRNAs for RPL11, which in other cell types has no effect on p53 levels, or RPL7a, which is known to induce p53 stabilization in a RPL11 dependent manner. We generated stable cell lines of inducible shRNAs against RPL11 or RPL7a using a tetracycline (Tet)-regulated miR30-shRNA system, TRMPVIR retroviral vector. By titrating doxycycline, we achieved ∼50% reduction of RPL11 or RPL7a transcript levels, with Renilla shRNA (Ren) as a control. A 50% depletion of RPL11 or RPL7a mRNAs led to an equal reduction in protein synthesis and ribosome biogenesis, however, RPL11 depletion did not alter p53 levels, whereas RPL7a mRNA depletion induced p53 stabilization and Caspase-3 dependent apoptosis. RPL7A or RPL11 depletion reduced cell proliferation to half that of control cells, with more cell death observed in RPL7a depleted cells versus RPL11 depleted cells. Treatment of RPL7a depleted cells with the caspase inhibitor ZVAD, or depletion of RPL7a in a p53 negative background suppressed cell death. Expression levels of the anti-apoptotic protein Mcl-1 were elevated in Eμ-Myc cells and unchanged in RPL11 depleted cells, but reduced in RPL7a depleted cells in a p53-dependent manner. This suggests that in RPL7a depleted cells, p53 regulates Mcl-1 levels to promote cell death and tumor suppression. Finally, immunoprecipitation of Mdm2 revealed the presence of L5/L11/5S-MIC in RPL7a depleted cells, but not in RPL11 depleted cells. Although p53 was not induced in RPL11 depleted cells, reduction of RPL11 to ∼95% led to acute cell death in both p53-/- and p53 +/+ Eμ-Myc cells, likely due to the inhibition of global translation. These findings demonstrate a differential abrogation of ribosome biogenesis by partial depletion of two essential RPs, which assemble at a very similar stage in 60S ribosome. For RPL7a, it led to L5/L11/5S-MIC induced p53 mediated cell death, and this was not the case for RPL11 as it is an essential component of the complex. Citation Format: Suresh Peddigari, Carol Mercer, Sara Kozma, George Thomas. c-Myc driven B cell lymphomas: role of the RPL5/RPL11/5S rRNA-MDM2 inhibitory complex (L5/L11/5S-MIC). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2024. doi:10.1158/1538-7445.AM2015-2024

Sara C. Kozma - One of the best experts on this subject based on the ideXlab platform.

  • Abstract 2024: c-Myc driven B cell lymphomas: role of the RPL5/RPL11/5S rRNA-MDM2 inhibitory complex (L5/L11/5S-MIC)
    Molecular and Cellular Biology, 2015
    Co-Authors: Suresh Peddigari, Carol A. Mercer, Sara C. Kozma, George Thomas
    Abstract:

    We recently demonstrated that as a consequence of impaired ribosome biogenesis, the L5/L11/5S pre-ribosomal complex is redirected to inhibit Mdm2, leading to p53 stabilization (Donati et al., 2013). In seminal studies, Eμ-Myc mice were crossed into a hypomorphic ribosomal protein (RP) L24 mutant background, which brought global translation rates to normal and extended their disease-free survival, independent of p53 (Barna et. al. 2008). However, when this mouse model harbors a single point mutation of Mdm2, which cannot bind the L5/L11/5S-MIC, mice succumb to lymphomagenesis much more rapidly than wild type Mdm2 mice (Macias et al, 2010). Moreover, inhibition of Pol I, which selectively transcribes rRNA genes, suppresses Myc driven tumors, potentially through the same L5/L11/5S-MIC (Bywater, et al, 2012). To address the role of the L5/L11/5S-MIC versus that of global translation in the Eμ-Myc B cell lymphocytes, we partially depleted mRNAs for RPL11, which in other cell types has no effect on p53 levels, or RPL7a, which is known to induce p53 stabilization in a RPL11 dependent manner. We generated stable cell lines of inducible shRNAs against RPL11 or RPL7a using a tetracycline (Tet)-regulated miR30-shRNA system, TRMPVIR retroviral vector. By titrating doxycycline, we achieved ∼50% reduction of RPL11 or RPL7a transcript levels, with Renilla shRNA (Ren) as a control. A 50% depletion of RPL11 or RPL7a mRNAs led to an equal reduction in protein synthesis and ribosome biogenesis, however, RPL11 depletion did not alter p53 levels, whereas RPL7a mRNA depletion induced p53 stabilization and Caspase-3 dependent apoptosis. RPL7A or RPL11 depletion reduced cell proliferation to half that of control cells, with more cell death observed in RPL7a depleted cells versus RPL11 depleted cells. Treatment of RPL7a depleted cells with the caspase inhibitor ZVAD, or depletion of RPL7a in a p53 negative background suppressed cell death. Expression levels of the anti-apoptotic protein Mcl-1 were elevated in Eμ-Myc cells and unchanged in RPL11 depleted cells, but reduced in RPL7a depleted cells in a p53-dependent manner. This suggests that in RPL7a depleted cells, p53 regulates Mcl-1 levels to promote cell death and tumor suppression. Finally, immunoprecipitation of Mdm2 revealed the presence of L5/L11/5S-MIC in RPL7a depleted cells, but not in RPL11 depleted cells. Although p53 was not induced in RPL11 depleted cells, reduction of RPL11 to ∼95% led to acute cell death in both p53-/- and p53 +/+ Eμ-Myc cells, likely due to the inhibition of global translation. These findings demonstrate a differential abrogation of ribosome biogenesis by partial depletion of two essential RPs, which assemble at a very similar stage in 60S ribosome. For RPL7a, it led to L5/L11/5S-MIC induced p53 mediated cell death, and this was not the case for RPL11 as it is an essential component of the complex. Citation Format: Suresh Peddigari, Carol Mercer, Sara Kozma, George Thomas. c-Myc driven B cell lymphomas: role of the RPL5/RPL11/5S rRNA-MDM2 inhibitory complex (L5/L11/5S-MIC). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2024. doi:10.1158/1538-7445.AM2015-2024

  • abstract 2024 c myc driven b cell lymphomas role of the rpl5 rpl11 5s rrna mdm2 inhibitory complex l5 l11 5s mic
    Cancer Research, 2015
    Co-Authors: Suresh Peddigari, Carol A. Mercer, Sara C. Kozma, George Thomas
    Abstract:

    We recently demonstrated that as a consequence of impaired ribosome biogenesis, the L5/L11/5S pre-ribosomal complex is redirected to inhibit Mdm2, leading to p53 stabilization (Donati et al., 2013). In seminal studies, Eμ-Myc mice were crossed into a hypomorphic ribosomal protein (RP) L24 mutant background, which brought global translation rates to normal and extended their disease-free survival, independent of p53 (Barna et. al. 2008). However, when this mouse model harbors a single point mutation of Mdm2, which cannot bind the L5/L11/5S-MIC, mice succumb to lymphomagenesis much more rapidly than wild type Mdm2 mice (Macias et al, 2010). Moreover, inhibition of Pol I, which selectively transcribes rRNA genes, suppresses Myc driven tumors, potentially through the same L5/L11/5S-MIC (Bywater, et al, 2012). To address the role of the L5/L11/5S-MIC versus that of global translation in the Eμ-Myc B cell lymphocytes, we partially depleted mRNAs for RPL11, which in other cell types has no effect on p53 levels, or RPL7a, which is known to induce p53 stabilization in a RPL11 dependent manner. We generated stable cell lines of inducible shRNAs against RPL11 or RPL7a using a tetracycline (Tet)-regulated miR30-shRNA system, TRMPVIR retroviral vector. By titrating doxycycline, we achieved ∼50% reduction of RPL11 or RPL7a transcript levels, with Renilla shRNA (Ren) as a control. A 50% depletion of RPL11 or RPL7a mRNAs led to an equal reduction in protein synthesis and ribosome biogenesis, however, RPL11 depletion did not alter p53 levels, whereas RPL7a mRNA depletion induced p53 stabilization and Caspase-3 dependent apoptosis. RPL7A or RPL11 depletion reduced cell proliferation to half that of control cells, with more cell death observed in RPL7a depleted cells versus RPL11 depleted cells. Treatment of RPL7a depleted cells with the caspase inhibitor ZVAD, or depletion of RPL7a in a p53 negative background suppressed cell death. Expression levels of the anti-apoptotic protein Mcl-1 were elevated in Eμ-Myc cells and unchanged in RPL11 depleted cells, but reduced in RPL7a depleted cells in a p53-dependent manner. This suggests that in RPL7a depleted cells, p53 regulates Mcl-1 levels to promote cell death and tumor suppression. Finally, immunoprecipitation of Mdm2 revealed the presence of L5/L11/5S-MIC in RPL7a depleted cells, but not in RPL11 depleted cells. Although p53 was not induced in RPL11 depleted cells, reduction of RPL11 to ∼95% led to acute cell death in both p53-/- and p53 +/+ Eμ-Myc cells, likely due to the inhibition of global translation. These findings demonstrate a differential abrogation of ribosome biogenesis by partial depletion of two essential RPs, which assemble at a very similar stage in 60S ribosome. For RPL7a, it led to L5/L11/5S-MIC induced p53 mediated cell death, and this was not the case for RPL11 as it is an essential component of the complex. Citation Format: Suresh Peddigari, Carol Mercer, Sara Kozma, George Thomas. c-Myc driven B cell lymphomas: role of the RPL5/RPL11/5S rRNA-MDM2 inhibitory complex (L5/L11/5S-MIC). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2024. doi:10.1158/1538-7445.AM2015-2024

Jingwei Cheng - One of the best experts on this subject based on the ideXlab platform.

  • merkel cell polyomavirus recruits mycl to the ep400 complex to promote oncogenesis
    PLOS Pathogens, 2017
    Co-Authors: Christian Berrios, Donglim Esther Park, Jingwei Cheng, Elizabeth A White, Reety Arora, Rosa Yoon, Timothy Branigan, Tengfei Xiao, Thomas Westerling
    Abstract:

    Merkel cell carcinoma (MCC) frequently contains integrated copies of Merkel cell polyomavirus DNA that express a truncated form of Large T antigen (LT) and an intact Small T antigen (ST). While LT binds RB and inactivates its tumor suppressor function, it is less clear how ST contributes to MCC tumorigenesis. Here we show that ST binds specifically to the MYC homolog MYCL (L-MYC) and recruits it to the 15-component EP400 histone acetyltransferase and chromatin remodeling complex. We performed a large-scale immunoprecipitation for ST and identified co-precipitating proteins by mass spectrometry. In addition to protein phosphatase 2A (PP2A) subunits, we identified MYCL and its heterodimeric partner MAX plus the EP400 complex. Immunoprecipitation for MAX and EP400 complex components confirmed their association with ST. We determined that the ST-MYCL-EP400 complex binds together to specific gene promoters and activates their expression by integrating chromatin immunoprecipitation with sequencing (ChIP-seq) and RNA-seq. MYCL and EP400 were required for maintenance of cell viability and cooperated with ST to promote gene expression in MCC cell lines. A genome-wide CRISPR-Cas9 screen confirmed the requirement for MYCL and EP400 in MCPyV-positive MCC cell lines. We demonstrate that ST can activate gene expression in a EP400 and MYCL dependent manner and this activity contributes to cellular transformation and generation of induced pluripotent stem cells.

  • merkel cell polyomavirus small t antigen promotes pro glycolytic metabolic perturbations required for transformation
    PLOS Pathogens, 2016
    Co-Authors: Christian Berrios, Megha Padi, Mark A Keibler, Donglim Esther Park, Vadim Molla, Jingwei Cheng, Gregory Stephanopoulos, John Quackenbush, James A Decaprio
    Abstract:

    Merkel cell polyomavirus (MCPyV) is an etiological agent of Merkel cell carcinoma (MCC), a highly aggressive skin cancer. The MCPyV small tumor antigen (ST) is required for maintenance of MCC and can transform normal cells. To gain insight into cellular perturbations induced by MCPyV ST, we performed transcriptome analysis of normal human fibroblasts with inducible expression of ST. MCPyV ST dynamically alters the cellular transcriptome with increased levels of glycolytic genes, including the monocarboxylate lactate transporter SLC16A1 (MCT1). Extracellular flux analysis revealed increased lactate export reflecting elevated aerobic glycolysis in ST expressing cells. Inhibition of MCT1 activity suppressed the growth of MCC cell lines and impaired MCPyV-dependent transformation of IMR90 cells. Both NF-κB and MYC have been shown to regulate MCT1 expression. While MYC was required for MCT1 induction, MCPyV-induced MCT1 levels decreased following knockdown of the NF-κB subunit RelA, supporting a synergistic activity between MCPyV and MYC in regulating MCT1 levels. Several MCC lines had high levels of MYCL and MYCN but not MYC. Increased levels of MYCL was more effective than MYC or MYCN in increasing extracellular acidification in MCC cells. Our results demonstrate the effects of MCPyV ST on the cellular transcriptome and reveal that transformation is dependent, at least in part, on elevated aerobic glycolysis.