The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Larry H Matherly - One of the best experts on this subject based on the ideXlab platform.
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transcriptional regulation of the human reduced folate carrier promoter c synergistic transactivation by sp1 and c ebp β and identification of a downstream repressor
Biochimica et Biophysica Acta, 2005Co-Authors: Scott G Payton, Johnathan R Whetstine, Larry H MatherlyAbstract:Abstract The human reduced folate carrier (hRFC) is ubiquitously but differentially expressed in human tissues and its levels are regulated by up to six alternatively spliced non-coding regions (designated A1/A2, A, B, C, D, and E) and by at least four promoters. By transient transfections of HepG2 human hepatoma cells with 5′ and 3′ deletion constructs spanning 2883 bp of upstream sequence, a transcriptionally important region was localized to within 177 bp flanking the transcriptional start sites for exon C. By gel shift and chromatin immunoprecipitation assays, Sp1 and C/EBP β transcription factors were found to bind consensus elements (GC-Box, CCAAT-Box) within this region. The functional importance of these elements was confirmed by transient tranfections of HepG2 cells with hRFC-C reporter constructs in which these elements were mutated, and by co-transfections of Drosophila SL-2 cells with wild-type hRFC-C promoter and expression constructs for Sp1 and C/EBP β. Whereas both Sp1 and C/EBP β transactivated hRFC-C promoter activity, C/EBP α and γ were transcriptionally inert. Sp1 combined with C/EBP β resulted in a synergistic transactivation. In HepG2 cells, transfections with Sp1 and C/EBP β both increased endogenous levels of hRFC-C transcripts. By 3′ deletion analysis, a repressor sequence was localized to within 71 bp flanking the minimal promoter. On gel shifts, a novel transcriptional repressor was localized to within 30 bp. Collectively, these results identify transcriptionally important regions in the hRFC-C minimal promoter that include a GC-Box and CCAAT-Box, and suggest that cooperative interactions between Sp1 and C/EBP β are essential for hRFC-C transactivation. Another possible factor in the tissue-specific regulation of the hRFC-C region involves the downstream repressor flanking the minimal promoter.
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roles of usf ikaros and sp proteins in the transcriptional regulation of the human reduced folate carrier b promoter
Biochemical Journal, 2004Co-Authors: Mingjun Liu, Johnathan R Whetstine, Scott G Payton, Robin M Flatley, Larry H MatherlyAbstract:The hRFC (human reduced folate carrier) is ubiquitously but differentially expressed in human tissues and its levels are regulated by up to seven non-coding regions (A1, A2, A, B, C, D and E) and at least four promoters. For the hRFC-B basal promoter, regulation involves binding of Sp (specificity protein) transcription factors to a critical GC-Box. By transiently transfecting HT1080 cells with 5′- and 3′-deletion constructs spanning 1057 bp of upstream sequence, a transcriptionally important region was localized to 158 bp flanking the transcriptional start sites. By gel shift and chromatin immunoprecipitation assays, USF (upstream stimulatory factor), Sp1 and Ikaros-related proteins were bound to consensus elements (one E-Box, two GC-Box and three Ikaros) within this region. The functional importance of these elements was confirmed by transient tranfections of HT1080 cells with hRFC-B reporter constructs in which they were mutated, and by co-transfections of Drosophila Mel-2 cells with wild-type hRFC-B promoter and expression constructs for USF1, USF2a, Sp1 and Ikaros 2 and 8. Both USF1 and Sp1 proteins transactivated the hRFC-B promoter. Sp1 combined with USF1 resulted in a synergistic transactivation. Identical results were obtained with USF2a. Ikaros 2 was a repressor of hRFC-B promoter activity whose effects were partly reversed by the dominant-negative Ikaros 8. In HT1080 cells, transfection with Ikaros 2 decreased endogenous hRFC-B transcripts, whereas USF1 and Sp1 increased transcript levels. Ikaros 2 also decreased reporter gene activity and levels of acetylated chromatin associated with the endogenous promoter. Collectively, these results identify transcriptionally important regions in the hRFC-B promoter that include multiple GC-Box, Ikaros and E-Box elements. Our results also suggest that co-operative interactions between transcription factors Sp1 and USF are essential for high-level hRFC-B transactivation and imply that these effects are modulated by the family of Ikaros proteins and by histone acetylation.
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the basal promoters for the human reduced folate carrier gene are regulated by a GC Box and a camp response element ap 1 like element basis for tissue specific gene expression
Journal of Biological Chemistry, 2001Co-Authors: Johnathan R Whetstine, Larry H MatherlyAbstract:Our laboratory previously identified two functional promoters (designated A and B) for the human reduced folate carrier (hRFC) gene that result in hRFC transcripts with differing 5′-untranslated regions. By transiently transfecting HT1080 and HepG2 cells with a series of 5′ and 3′ deletions in the hRFC-B and -A promoters, the minimal promoters were localized within 46 and 47 base pairs, respectively. Gel mobility shift assays with the hRFC-B basal promoter region revealed specific DNA-protein complexes involving a highly conserved GC-Box and Sp1 or Sp3. In Drosophila SL2 cells, both Sp1 and the long Sp3 isoform potently transactivated the hRFC-B basal promoter; however, the short Sp3 isoforms were transcriptionally inert and resulted in a potent inhibition of Sp1 transactivation. For the hRFC-A basal promoter, a CRE/AP-1-like element was bound by the bZip superfamily of DNA-binding proteins. Cell-specific DNA-protein complexes were identified for hRFC-A (CREB-1 and c-Jun in HT1080 cells; CREB-1 and ATF-1 in HepG2 cells). When the GC-Box and CRE/AP-1-like elements were mutated, a 60–90% decrease in promoter activity was observed in both cell lines. These results identify the critical regulatory regions for the hRFC basal promoters and stress the functional importance of the Sp and bZip families of transcription factors in regulating hRFC expression.
Ryuichi Okayasu - One of the best experts on this subject based on the ideXlab platform.
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dna topoisomerase inhibitor etoposide enhances GC Box dependent promoter activity via sp1 phosphorylation
Cancer Science, 2007Co-Authors: Ichiro Niina, Takayuki Torigoe, Tomonori Igarashi, Tetsuro Wakasugi, Naoya Miyamoto, Tetsuro Onitsuka, Hiroto Izumi, Masaki Shiota, Takeshi Uchiumi, Ryuichi OkayasuAbstract:Modification of transcription factors by anticancer agents plays an important role in both apoptotic and survival signaling. Here we report that both DNA topoisomerase I and II inhibitors such as SN-38 and etoposide, but not cisplatin, 5-fluorouracil or actinomycin D, can induce phosphorylation of the transcription factor Sp1. Furthermore, DNA topoisomerase inhibitors were shown to transactivate GC-Box-dependent promoters such as the SV40 and vascular endothelial growth factor promoters. The phosphorylated form of Sp1 was detectable within 30 min of etoposide treatment and was greatly diminished by the presence of the PI3K inhibitor wortmannin and by DNA-dependent protein kinase (DNA-PK) knockdown. We also confirmed that the phosphorylated form of DNA-PK was increased by treatment with both etoposide and SN-38. Taken together, these findings demonstrate a novel genomic response to anticancer agents that induce Sp1 phosphorylation, and might contribute to tumor progression and drug resistance. (Cancer Sci 2007; 98: 858–863)
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dna topoisomerase inhibitor etoposide enhances GC Box dependent promoter activity via sp1 phosphorylation
Cancer Science, 2007Co-Authors: Ichiro Niina, Takayuki Torigoe, Tomonori Igarashi, Tetsuro Wakasugi, Naoya Miyamoto, Hiroto Izumi, Masaki Shiota, Takeshi Uchiumi, Takamitsu Onitsuka, Ryuichi OkayasuAbstract:Modification of transcription factors by anticancer agents plays an important role in both apoptotic and survival signaling. Here we report that both DNA topoisomerase I and II inhibitors such as SN-38 and etoposide, but not cisplatin, 5-fluorouracil or actinomycin D, can induce phosphorylation of the transcription factor Sp1. Furthermore, DNA topoisomerase inhibitors were shown to transactivate GC-Box-dependent promoters such as the SV40 and vascular endothelial growth factor promoters. The phosphorylated form of Sp1 was detectable within 30 min of etoposide treatment and was greatly diminished by the presence of the PI3K inhibitor wortmannin and by DNA-dependent protein kinase (DNA-PK) knockdown. We also confirmed that the phosphorylated form of DNA-PK was increased by treatment with both etoposide and SN-38. Taken together, these findings demonstrate a novel genomic response to anticancer agents that induce Sp1 phosphorylation, and might contribute to tumor progression and drug resistance.
Ichiro Niina - One of the best experts on this subject based on the ideXlab platform.
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dna topoisomerase inhibitor etoposide enhances GC Box dependent promoter activity via sp1 phosphorylation
Cancer Science, 2007Co-Authors: Ichiro Niina, Takayuki Torigoe, Tomonori Igarashi, Tetsuro Wakasugi, Naoya Miyamoto, Tetsuro Onitsuka, Hiroto Izumi, Masaki Shiota, Takeshi Uchiumi, Ryuichi OkayasuAbstract:Modification of transcription factors by anticancer agents plays an important role in both apoptotic and survival signaling. Here we report that both DNA topoisomerase I and II inhibitors such as SN-38 and etoposide, but not cisplatin, 5-fluorouracil or actinomycin D, can induce phosphorylation of the transcription factor Sp1. Furthermore, DNA topoisomerase inhibitors were shown to transactivate GC-Box-dependent promoters such as the SV40 and vascular endothelial growth factor promoters. The phosphorylated form of Sp1 was detectable within 30 min of etoposide treatment and was greatly diminished by the presence of the PI3K inhibitor wortmannin and by DNA-dependent protein kinase (DNA-PK) knockdown. We also confirmed that the phosphorylated form of DNA-PK was increased by treatment with both etoposide and SN-38. Taken together, these findings demonstrate a novel genomic response to anticancer agents that induce Sp1 phosphorylation, and might contribute to tumor progression and drug resistance. (Cancer Sci 2007; 98: 858–863)
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dna topoisomerase inhibitor etoposide enhances GC Box dependent promoter activity via sp1 phosphorylation
Cancer Science, 2007Co-Authors: Ichiro Niina, Takayuki Torigoe, Tomonori Igarashi, Tetsuro Wakasugi, Naoya Miyamoto, Hiroto Izumi, Masaki Shiota, Takeshi Uchiumi, Takamitsu Onitsuka, Ryuichi OkayasuAbstract:Modification of transcription factors by anticancer agents plays an important role in both apoptotic and survival signaling. Here we report that both DNA topoisomerase I and II inhibitors such as SN-38 and etoposide, but not cisplatin, 5-fluorouracil or actinomycin D, can induce phosphorylation of the transcription factor Sp1. Furthermore, DNA topoisomerase inhibitors were shown to transactivate GC-Box-dependent promoters such as the SV40 and vascular endothelial growth factor promoters. The phosphorylated form of Sp1 was detectable within 30 min of etoposide treatment and was greatly diminished by the presence of the PI3K inhibitor wortmannin and by DNA-dependent protein kinase (DNA-PK) knockdown. We also confirmed that the phosphorylated form of DNA-PK was increased by treatment with both etoposide and SN-38. Taken together, these findings demonstrate a novel genomic response to anticancer agents that induce Sp1 phosphorylation, and might contribute to tumor progression and drug resistance.
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dna topoisomerase ii poison tas 103 transactivates GC Box dependent transcription via acetylation of sp1
Journal of Biological Chemistry, 2005Co-Authors: Takayuki Torigoe, Ichiro Niina, Tomonori Igarashi, Tetsuro Wakasugi, Hiroto Izumi, Takeshi Yoshida, Izumi Shibuya, Kazuo Chijiiwa, Kenichi Matsuo, Hideaki ItohAbstract:Drug-induced modifications of transcription factors play important roles in both apoptosis and survival signaling. The data presented here show that the DNA topoisomerase II poison TAS-103 transactivated the SV40 promoter in a GC-Box-dependent manner and induced Sp1 acetylation in cells expressing p300. This activity was not observed in cells lacking p300. TAS-103 treatment also enhanced the p300 content of the nucleus and the interaction of p300 with Sp1. Cellular susceptibility to TAS-103 was correlated with p300 expression but not with topoisomerase II expression. Furthermore, the presence of p300 significantly sensitized cancer cells to TAS-103 but not to cisplatin. Taken together, these findings demonstrate novel genomic responses to anticancer agents that modulate Sp1 acetylation and Sp1-dependent transcription in an apoptotic pathway.
Takayuki Torigoe - One of the best experts on this subject based on the ideXlab platform.
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dna topoisomerase inhibitor etoposide enhances GC Box dependent promoter activity via sp1 phosphorylation
Cancer Science, 2007Co-Authors: Ichiro Niina, Takayuki Torigoe, Tomonori Igarashi, Tetsuro Wakasugi, Naoya Miyamoto, Tetsuro Onitsuka, Hiroto Izumi, Masaki Shiota, Takeshi Uchiumi, Ryuichi OkayasuAbstract:Modification of transcription factors by anticancer agents plays an important role in both apoptotic and survival signaling. Here we report that both DNA topoisomerase I and II inhibitors such as SN-38 and etoposide, but not cisplatin, 5-fluorouracil or actinomycin D, can induce phosphorylation of the transcription factor Sp1. Furthermore, DNA topoisomerase inhibitors were shown to transactivate GC-Box-dependent promoters such as the SV40 and vascular endothelial growth factor promoters. The phosphorylated form of Sp1 was detectable within 30 min of etoposide treatment and was greatly diminished by the presence of the PI3K inhibitor wortmannin and by DNA-dependent protein kinase (DNA-PK) knockdown. We also confirmed that the phosphorylated form of DNA-PK was increased by treatment with both etoposide and SN-38. Taken together, these findings demonstrate a novel genomic response to anticancer agents that induce Sp1 phosphorylation, and might contribute to tumor progression and drug resistance. (Cancer Sci 2007; 98: 858–863)
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dna topoisomerase inhibitor etoposide enhances GC Box dependent promoter activity via sp1 phosphorylation
Cancer Science, 2007Co-Authors: Ichiro Niina, Takayuki Torigoe, Tomonori Igarashi, Tetsuro Wakasugi, Naoya Miyamoto, Hiroto Izumi, Masaki Shiota, Takeshi Uchiumi, Takamitsu Onitsuka, Ryuichi OkayasuAbstract:Modification of transcription factors by anticancer agents plays an important role in both apoptotic and survival signaling. Here we report that both DNA topoisomerase I and II inhibitors such as SN-38 and etoposide, but not cisplatin, 5-fluorouracil or actinomycin D, can induce phosphorylation of the transcription factor Sp1. Furthermore, DNA topoisomerase inhibitors were shown to transactivate GC-Box-dependent promoters such as the SV40 and vascular endothelial growth factor promoters. The phosphorylated form of Sp1 was detectable within 30 min of etoposide treatment and was greatly diminished by the presence of the PI3K inhibitor wortmannin and by DNA-dependent protein kinase (DNA-PK) knockdown. We also confirmed that the phosphorylated form of DNA-PK was increased by treatment with both etoposide and SN-38. Taken together, these findings demonstrate a novel genomic response to anticancer agents that induce Sp1 phosphorylation, and might contribute to tumor progression and drug resistance.
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dna topoisomerase ii poison tas 103 transactivates GC Box dependent transcription via acetylation of sp1
Journal of Biological Chemistry, 2005Co-Authors: Takayuki Torigoe, Ichiro Niina, Tomonori Igarashi, Tetsuro Wakasugi, Hiroto Izumi, Takeshi Yoshida, Izumi Shibuya, Kazuo Chijiiwa, Kenichi Matsuo, Hideaki ItohAbstract:Drug-induced modifications of transcription factors play important roles in both apoptosis and survival signaling. The data presented here show that the DNA topoisomerase II poison TAS-103 transactivated the SV40 promoter in a GC-Box-dependent manner and induced Sp1 acetylation in cells expressing p300. This activity was not observed in cells lacking p300. TAS-103 treatment also enhanced the p300 content of the nucleus and the interaction of p300 with Sp1. Cellular susceptibility to TAS-103 was correlated with p300 expression but not with topoisomerase II expression. Furthermore, the presence of p300 significantly sensitized cancer cells to TAS-103 but not to cisplatin. Taken together, these findings demonstrate novel genomic responses to anticancer agents that modulate Sp1 acetylation and Sp1-dependent transcription in an apoptotic pathway.
Tetsuro Wakasugi - One of the best experts on this subject based on the ideXlab platform.
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dna topoisomerase inhibitor etoposide enhances GC Box dependent promoter activity via sp1 phosphorylation
Cancer Science, 2007Co-Authors: Ichiro Niina, Takayuki Torigoe, Tomonori Igarashi, Tetsuro Wakasugi, Naoya Miyamoto, Tetsuro Onitsuka, Hiroto Izumi, Masaki Shiota, Takeshi Uchiumi, Ryuichi OkayasuAbstract:Modification of transcription factors by anticancer agents plays an important role in both apoptotic and survival signaling. Here we report that both DNA topoisomerase I and II inhibitors such as SN-38 and etoposide, but not cisplatin, 5-fluorouracil or actinomycin D, can induce phosphorylation of the transcription factor Sp1. Furthermore, DNA topoisomerase inhibitors were shown to transactivate GC-Box-dependent promoters such as the SV40 and vascular endothelial growth factor promoters. The phosphorylated form of Sp1 was detectable within 30 min of etoposide treatment and was greatly diminished by the presence of the PI3K inhibitor wortmannin and by DNA-dependent protein kinase (DNA-PK) knockdown. We also confirmed that the phosphorylated form of DNA-PK was increased by treatment with both etoposide and SN-38. Taken together, these findings demonstrate a novel genomic response to anticancer agents that induce Sp1 phosphorylation, and might contribute to tumor progression and drug resistance. (Cancer Sci 2007; 98: 858–863)
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dna topoisomerase inhibitor etoposide enhances GC Box dependent promoter activity via sp1 phosphorylation
Cancer Science, 2007Co-Authors: Ichiro Niina, Takayuki Torigoe, Tomonori Igarashi, Tetsuro Wakasugi, Naoya Miyamoto, Hiroto Izumi, Masaki Shiota, Takeshi Uchiumi, Takamitsu Onitsuka, Ryuichi OkayasuAbstract:Modification of transcription factors by anticancer agents plays an important role in both apoptotic and survival signaling. Here we report that both DNA topoisomerase I and II inhibitors such as SN-38 and etoposide, but not cisplatin, 5-fluorouracil or actinomycin D, can induce phosphorylation of the transcription factor Sp1. Furthermore, DNA topoisomerase inhibitors were shown to transactivate GC-Box-dependent promoters such as the SV40 and vascular endothelial growth factor promoters. The phosphorylated form of Sp1 was detectable within 30 min of etoposide treatment and was greatly diminished by the presence of the PI3K inhibitor wortmannin and by DNA-dependent protein kinase (DNA-PK) knockdown. We also confirmed that the phosphorylated form of DNA-PK was increased by treatment with both etoposide and SN-38. Taken together, these findings demonstrate a novel genomic response to anticancer agents that induce Sp1 phosphorylation, and might contribute to tumor progression and drug resistance.
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dna topoisomerase ii poison tas 103 transactivates GC Box dependent transcription via acetylation of sp1
Journal of Biological Chemistry, 2005Co-Authors: Takayuki Torigoe, Ichiro Niina, Tomonori Igarashi, Tetsuro Wakasugi, Hiroto Izumi, Takeshi Yoshida, Izumi Shibuya, Kazuo Chijiiwa, Kenichi Matsuo, Hideaki ItohAbstract:Drug-induced modifications of transcription factors play important roles in both apoptosis and survival signaling. The data presented here show that the DNA topoisomerase II poison TAS-103 transactivated the SV40 promoter in a GC-Box-dependent manner and induced Sp1 acetylation in cells expressing p300. This activity was not observed in cells lacking p300. TAS-103 treatment also enhanced the p300 content of the nucleus and the interaction of p300 with Sp1. Cellular susceptibility to TAS-103 was correlated with p300 expression but not with topoisomerase II expression. Furthermore, the presence of p300 significantly sensitized cancer cells to TAS-103 but not to cisplatin. Taken together, these findings demonstrate novel genomic responses to anticancer agents that modulate Sp1 acetylation and Sp1-dependent transcription in an apoptotic pathway.
