-
[show abstract]
[hide abstract]
ABSTRACT: The cap-binding complex (CBC) binds to the cap structure of mRNA to protect it from exonucleases as well as to regulate downstream post-transcriptional events, translational initiation and nonsense-mediated mRNA decay. However, its role in regulation of the upstream transcriptional events such as initiation or elongation remains unknown. Here, using a formaldehyde-based in vivo cross-linking and chromatin immunoprecipitation assay in conjunction with transcriptional, mutational and co-immunoprecipitational analyses, we show that CBC is recruited to the body of yeast gene, and then stimulates the formation of pre-initiation complex (PIC) at several yeast promoters through its interaction with Mot1p (modifier of transcription). Mot1p is recruited to these promoters, and enhances the PIC formation. We find that CBC promotes the recruitment of Mot1p which subsequently stimulates PIC formation at these promoters. Furthermore, the formation of PIC is essential for recruitment of CBC. Thus, our study presents an interesting observation that an mRNA binding factor exhibits a reciprocal synergistic effect on formation of PIC (and hence transcriptional initiation) at the promoter, revealing a new pathway of eukaryotic gene regulation in vivo.
Nucleic Acids Research 11/2010; 39(6):2188-209. · 8.03 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Histone acetylation has been shown to be required for the proper regulation of many cellular processes including transcription, DNA repair, and chromatin assembly. Acetylation of histone H3 on lysine 56 (H3K56) occurs both during the premeiotic and mitotic S phase and persists throughout DNA damage repair. To learn more about the molecular mechanism of H3K56 acetylation and factors required for this process, we surveyed the genome of the yeast Saccharomyces cerevisiae to identify genes necessary for this process. A comparative global proteomic screen identified several factors required for global H3K56 acetylation, which included histone chaperone Asf1 and a protein of an unknown function Rtt109 but not Spt10. Our results indicate that the loss of Rtt109 results in the loss of H3K56 acetylation, both on bulk histone and on chromatin, similar to that of asf1Delta or the K56Q mutation. RTT109 deletion exhibits sensitivity to DNA damaging agents similar to that of asf1Delta and H3K56Q mutants. Furthermore, Rtt109 and H3K56 acetylation appear to correlate with actively transcribed genes and associate with the elongating form of polymerase II in yeast. This histone modification is also associated with some of the transcriptionally active puff sites in Drosophila. Our results indicate a new role for the Rtt109 protein in the proper regulation of H3K56 acetylation.
Journal of Biological Chemistry 01/2007; 281(49):37270-4. · 4.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Histone acetylation has been shown to be required for the proper regulation of many cellular processes including transcription,
DNA repair, and chromatin assembly. Acetylation of histone H3 on lysine 56 (H3K56) occurs both during the premeiotic and mitotic
S phase and persists throughout DNA damage repair. To learn more about the molecular mechanism of H3K56 acetylation and factors
required for this process, we surveyed the genome of the yeast Saccharomyces cerevisiae to identify genes necessary for this process. A comparative global proteomic screen identified several factors required for
global H3K56 acetylation, which included histone chaperone Asf1 and a protein of an unknown function Rtt109 but not Spt10.
Our results indicate that the loss of Rtt109 results in the loss of H3K56 acetylation, both on bulk histone and on chromatin,
similar to that of asf1Δ or the K56Q mutation. RTT109 deletion exhibits sensitivity to DNA damaging agents similar to that of asf1Δ and H3K56Q mutants. Furthermore, Rtt109 and H3K56 acetylation appear to correlate with actively transcribed genes and associate
with the elongating form of polymerase II in yeast. This histone modification is also associated with some of the transcriptionally
active puff sites in Drosophila. Our results indicate a new role for the Rtt109 protein in the proper regulation of H3K56 acetylation.
Journal of Biological Chemistry 12/2006; 281(49):37270-37274. · 4.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Although Sgf73p, a yeast homologue of human Sca7p, has recently been implicated as a new component of Spt-Ada-Gcn5-acetyltransferase (SAGA), its association with SAGA and functional role in regulation of transcription remain unknown in vivo. Here, using a chromatin immunoprecipitation (ChIP) assay, we show in vivo that, like SAGA, Sgf73p is recruited to the upstream activating sequence (UAS) of a SAGA-dependent gene, GAL1, in an activator-dependent manner. Further, Sgf73p is required for recruitment of SAGA to the GAL1 UAS, and facilitates formation of the preinitiation complex (PIC) assembly at the GAL1 promoter. When PIC is not formed in Deltasgf73, histone H3 is not evicted from the GAL1 promoter. Interestingly, PIC formation at GAL1 is not regulated by histone H3 acetylation or histone acetyltransferase (HAT) activity of SAGA. Similarly, Sgf73p facilitates PIC formation at another SAGA-dependent gene, ADH1, independent of histone H3 acetylation or HAT. In contrast, Sgf73p stimulates PIC formation at PHO84 (a SAGA-dependent gene), in a HAT-dependent-manner. Collectively, our data reveal that Sgf73p is required for SAGA recruitment, and stimulates PIC formation either in a HAT-dependent or -independent manner, providing significant information on how Sgf73p and possibly human Sca7p function physiologically.
Nucleic Acids Research 02/2006; 34(21):6225-32. · 8.03 Impact Factor
