The Experts below are selected from a list of 81 Experts worldwide ranked by ideXlab platform
Emine Ercikan Abali - One of the best experts on this subject based on the ideXlab platform.
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A second target of benzamide riboside: Dihydrofolate Reductase
Cancer biology & therapy, 2012Co-Authors: Breton Roussel, Kathleen W. Scotto, Debabrata Banerjee, Nadine Johnson-farley, John E. Kerrigan, Krzysztof Felczak, Krzysztof W. Pankiewicz, Murugesan Gounder, Hongxia Lin, Emine Ercikan AbaliAbstract:Dihydrofolate Reductase (DHFR) is an essential enzyme involved in de novo purine and thymidine biosynthesis. For several decades, selective inhibition of DHFR has proven to be a potent therapeutic ...
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Species-Specific Differences in Translational Regulation of Dihydrofolate Reductase
Molecular pharmacology, 2009Co-Authors: Yi-ching Hsieh, Joseph R. Bertino, Nancy E. Skacel, Nitu Bansal, Kathleen W. Scotto, Debabrata Banerjee, Emine Ercikan AbaliAbstract:We have observed that rodent cell lines (mouse, hamster) contain approximately 10 times the levels of Dihydrofolate Reductase as human cell lines, yet the sensitivity to methotrexate (ED50), the folate antagonist that targets this enzyme, is similar. Our previous studies showed that Dihydrofolate Reductase protein levels increased after methotrexate exposure, and we proposed that this increase was due to the relief of feedback inhibition of translation as a consequence of methotrexate binding to Dihydrofolate Reductase. In the current report, we show that unlike what was observed in human cells, Dihydrofolate Reductase (DHFR) levels do not increase in hamster cells after methotrexate exposure. We provide evidence to show that although there are differences in the putative mRNA structure between hamster and human mRNA in the Dihydrofolate Reductase binding region previously identified, “hamsterization” of this region in human Dihydrofolate Reductase mRNA did not change the level of the enzyme or its induction by methotrexate. Further experiments showed that human Dihydrofolate Reductase is a promiscuous enzyme and that it is the difference between the hamster and human Dihydrofolate Reductase protein, rather than the DHFR mRNA, that determines the response to methotrexate exposure. We also present evidence to suggest that the translational up-regulation of Dihydrofolate Reductase by methotrexate in tumor cells is an adaptive mechanism that decreases sensitivity to this drug.
Karen S. Anderson - One of the best experts on this subject based on the ideXlab platform.
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Kinetic reaction scheme for the Dihydrofolate Reductase domain of the bifunctional thymidylate synthase-Dihydrofolate Reductase from Leishmania major.
Biochemistry, 1998Co-Authors: Po-huang Liang, Karen S. AndersonAbstract:In several species of protozoa, the catalytic activities for the enzymes Dihydrofolate Reductase (DHFR) and thymidylate synthase (TS) reside on a single polypeptide chain constituting a bifunctional thymidylate synthase-Dihydrofolate Reductase enzyme. In most other species, however, these enzymes occur as monofunctional catalytic activities on separate enzymes. In this study, the kinetic reaction scheme for the Dihydrofolate Reductase activity from the bifunctional thymidylate synthase-Dihydrofolate Reductase (TS-DHFR) isolated from the parasite Leishmania major is compared to that of the monofunctional DHFR purified from Escherichia coli. Examination using pre-steady-state kinetic methods reveals interesting differences between the bifunctional and monofunctional forms of the Dihydrofolate Reductase enzymes. The rate-limiting step in the kinetic pathway for the monofunctional E. coli enzyme is the release of product, tetrahydrofolate. In contrast, for the L. major bifunctional enzyme, the kinetic step which limits the steady-state turnover is a conformational change associated with the release of NADP+. A complete kinetic description for the Dihydrofolate Reductase reaction pathway for the bifunctional enzyme is presented.
Carlos J. Ciudad - One of the best experts on this subject based on the ideXlab platform.
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An Intron Is Required for Dihydrofolate Reductase Protein Stability
The Journal of biological chemistry, 2003Co-Authors: Véronique Noé, Simon Mackenzie, Carlos J. CiudadAbstract:Abstract We compared the expression of Dihydrofolate Reductase minigenes with and without an intron. The levels of protein were significantly higher in the presence of Dihydrofolate Reductase intron 1. However, mRNA levels in both constructs were comparable. In addition, the RNA transcribed from either construct was correctly polyadenylated and exported to the cytoplasm. The intron-mediated increase in Dihydrofolate Reductase protein levels was position-independent and was also observed when Dihydrofolate Reductase intron 1 was replaced by heterologous introns. The translational rate of Dihydrofolate Reductase protein was increased in transfectants from the intron-containing minigene. In addition, the protein encoded by the intronless construct was unstable and subject to lysosomal degradation, thus showing a shorter half-life than the protein encoded by the intron-containing minigene. We conclude that an intron is required for the translation and stability of Dihydrofolate Reductase protein.
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Retinoblastoma protein associates with SP1 and activates the hamster Dihydrofolate Reductase promoter.
Oncogene, 1998Co-Authors: Cristina Alemany, Lawrence A Chasin, Carlos J. CiudadAbstract:Retinoblastoma protein associates with SP1 and activates the hamster Dihydrofolate Reductase promoter
Po-huang Liang - One of the best experts on this subject based on the ideXlab platform.
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Kinetic reaction scheme for the Dihydrofolate Reductase domain of the bifunctional thymidylate synthase-Dihydrofolate Reductase from Leishmania major.
Biochemistry, 1998Co-Authors: Po-huang Liang, Karen S. AndersonAbstract:In several species of protozoa, the catalytic activities for the enzymes Dihydrofolate Reductase (DHFR) and thymidylate synthase (TS) reside on a single polypeptide chain constituting a bifunctional thymidylate synthase-Dihydrofolate Reductase enzyme. In most other species, however, these enzymes occur as monofunctional catalytic activities on separate enzymes. In this study, the kinetic reaction scheme for the Dihydrofolate Reductase activity from the bifunctional thymidylate synthase-Dihydrofolate Reductase (TS-DHFR) isolated from the parasite Leishmania major is compared to that of the monofunctional DHFR purified from Escherichia coli. Examination using pre-steady-state kinetic methods reveals interesting differences between the bifunctional and monofunctional forms of the Dihydrofolate Reductase enzymes. The rate-limiting step in the kinetic pathway for the monofunctional E. coli enzyme is the release of product, tetrahydrofolate. In contrast, for the L. major bifunctional enzyme, the kinetic step which limits the steady-state turnover is a conformational change associated with the release of NADP+. A complete kinetic description for the Dihydrofolate Reductase reaction pathway for the bifunctional enzyme is presented.
Debabrata Banerjee - One of the best experts on this subject based on the ideXlab platform.
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A second target of benzamide riboside: Dihydrofolate Reductase
Cancer biology & therapy, 2012Co-Authors: Breton Roussel, Kathleen W. Scotto, Debabrata Banerjee, Nadine Johnson-farley, John E. Kerrigan, Krzysztof Felczak, Krzysztof W. Pankiewicz, Murugesan Gounder, Hongxia Lin, Emine Ercikan AbaliAbstract:Dihydrofolate Reductase (DHFR) is an essential enzyme involved in de novo purine and thymidine biosynthesis. For several decades, selective inhibition of DHFR has proven to be a potent therapeutic ...
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Species-Specific Differences in Translational Regulation of Dihydrofolate Reductase
Molecular pharmacology, 2009Co-Authors: Yi-ching Hsieh, Joseph R. Bertino, Nancy E. Skacel, Nitu Bansal, Kathleen W. Scotto, Debabrata Banerjee, Emine Ercikan AbaliAbstract:We have observed that rodent cell lines (mouse, hamster) contain approximately 10 times the levels of Dihydrofolate Reductase as human cell lines, yet the sensitivity to methotrexate (ED50), the folate antagonist that targets this enzyme, is similar. Our previous studies showed that Dihydrofolate Reductase protein levels increased after methotrexate exposure, and we proposed that this increase was due to the relief of feedback inhibition of translation as a consequence of methotrexate binding to Dihydrofolate Reductase. In the current report, we show that unlike what was observed in human cells, Dihydrofolate Reductase (DHFR) levels do not increase in hamster cells after methotrexate exposure. We provide evidence to show that although there are differences in the putative mRNA structure between hamster and human mRNA in the Dihydrofolate Reductase binding region previously identified, “hamsterization” of this region in human Dihydrofolate Reductase mRNA did not change the level of the enzyme or its induction by methotrexate. Further experiments showed that human Dihydrofolate Reductase is a promiscuous enzyme and that it is the difference between the hamster and human Dihydrofolate Reductase protein, rather than the DHFR mRNA, that determines the response to methotrexate exposure. We also present evidence to suggest that the translational up-regulation of Dihydrofolate Reductase by methotrexate in tumor cells is an adaptive mechanism that decreases sensitivity to this drug.