The Molecular Mechanism Of Transcription Regulation Of Ssa4 Gene By Reversible Acetylation In Yeast

The eukaryotic genome is packaged into chromatin, which acts as a constant barrier to transcription and other cellular processes that require access to DNA. Therefore the structure of chromatin has to be modified before active transcription can proceed. Gcn5 (general control non-derepressible 5) is the catalytic subunit of SAGA (Spt-Ada-Gcn5-acetyltransferase), a major transcription-related HAT complex in yeast. Histone H3 is the primary target for both of the complex, and the complex display significant functional redundancy. We chose ssa4 as the target gene for biochemical and molecular studies. Our results indicated that histone acetylation was required for the ssa4 transcription activation. Histone acetyltransferases (HATs) Gcn5 affecteds ssa4 gene transcription and its HAT activity was required for the function of regulating transcription. The transcriptional regulatory function of Gcn5 was direct because it could be recruited to ssa4 gene. The HATs modulated the transcription of ssa4 genes through affecting the acetylation status of histone H3. Our data also showed that the mRNA level of ssa4 gene was increased in the cells treated with TSA or the cells with the deletion of histone deacetylases (HDACs), indicating that HDACs were involved in the transcription of ssa4 gene. Data presented in this report provide further insight into and direct evidence of the functions of Gcn5 in hsp ssa4 gene transcriptional in yeast.