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Repression Activities (repression + activity)
Selected AbstractsRole of the N-terminal Region in the Function of the Photosynthetic Bacterium Transcription Regulator PpsR,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2008Yoichi Yamazaki PpsR is a transcription repressor for the gene cluster encoding photosystem genes in Rhodobacter sphaeroides. Repression activity is accomplished by DNA binding on the promoter regions of the photosystem gene clusters, and depends on both the redox potential and the presence of antirepressor protein AppA. To understand DNA repression regulation by PpsR, we investigated the function of PpsR domains in self-association for DNA binding. We constructed domain-deletion mutants and verified DNA-binding activity and dimer formation. Gel shift assay for measuring the DNA-binding activity of three sequential N-terminal deletion mutants revealed that N-terminal deletions (of minimum 121 residues) caused loss of binding activity. Size-exclusion gel chromatography revealed that deletion mutant which lacks the N-terminal 121-amino acid deletion mutant to exist as a dimer, although it was less stable than the intact PpsR. The mutants lacking the adjacent regions, Q-linker region and the first Per-Ant-Sim domain, did not form dimers, suggesting the involvement of the N-terminal region in dimer formation. This region is thus considered to be a functional domain in self-association, although not yet identified as a structural domain. Circular dichroism spectrum of the N-terminal region fragment exhibited a ,/, structure. We conclude that this region is a structural and functional domain, contributing to PpsR repression through dimer stabilization. [source] Distinct localizations and repression activities of MM-1 isoforms toward c-Myc,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2006Yuko Hagio Abstract MM-1 was identified as a c-Myc-binding protein and has been reported to repress the E-box-dependent transcription activity of c-Myc by recruiting HDAC1 complex via TIF1 ,/KAP1. In this study, originally isolated MM-1 was found to be a fusion protein comprised of the N-terminal 13 amino acids from the sequence of chromosome 14 and of the rest of the amino acids from that of chromosome 12 and was found to be expressed ubiquitously in all human tissues. Four splicing isoforms of MM-1, MM-1,, MM-1,, MM-1,, and MM-1,, which are derived from the sequence of chromosome 12, were then identified. Of these isoforms, MM-1,, MM-1,, and MM-1, were found to be expressed in tissue-specific manners and MM-1, was found to be expressed ubiquitously. Although all of the isoforms potentially possessed c-Myc- and TIF1,-binding activities, MM-1, and MM-1, were found to be mainly localized in the cytoplasm and MM-1, and MM-1, were found to be localized in the nucleus together with both c-Myc and TIF1,. Furthermore, when repression activities of MM-1 isoforms toward c-Myc transcription activity were examined by reporter gene assays in HeLa cells, MM-1,, MM-1,, and MM-1,, but not MM-1,, were found to repress transcription activity of c-Myc, and the degrees of repression by MM-1, and MM-1, were smaller than those by MM-1 and MM-1,. These results suggest that each MM-1 isoform distinctly regulates c-Myc transcription activity in respective tissues. J. Cell. Biochem. © 2005 Wiley-Liss, Inc. [source] Identification of a novel BTB-zinc finger transcriptional repressor, CIBZ, that interacts with CtBP corepressorGENES TO CELLS, Issue 9 2005Nobuhiro Sasai The transcriptional corepressor C-terminal binding protein (CtBP) is thought to be involved in development and oncogenesis, but the regulation of its corepressor activity is largely unknown. We show here that a novel BTB-zinc finger protein, CIBZ (CtBP-interacting BTB zinc finger protein; a mouse ortholog of rat ZENON that was recently identified as an e-box/dyad binding protein), redistributes CtBP to pericentromeric foci from a diffuse nuclear localization in interphase cells. CIBZ physically associates with CtBP via a conserved CtBP binding motif, PLDLR. When heterologously targeted to DNA, CIBZ represses transcription via two independent repression domains, an N-terminal BTB domain and a PLDLR motif-containing RD2 region, in a histone deacetylase-independent and -dependent manner, respectively. Mutation in the PLDLR motif abolishes the CIBZ-CtBP interaction and transcriptional repression activity of RD2, but does not affect the repression activity of the BTB domain. Furthermore, this PLDLR-mutated CIBZ cannot target CtBP to pericentromeric foci, although it is localized to the pericentromeric foci itself. These results suggest that at least one repression mechanism mediated by CIBZ is recruitment of the CtBP/HDAC complex to pericentromeric foci, and that CIBZ may regulate pericentromeric targeting of CtBP. [source] | ||||||||||