engleski

ChlPing of the SWI/SNF complex at the PHO5 promoter versus the PHO8 promoter in Saccharomyces cerevisiae

Among the PHO genes in the yeast Saccharomyces cerevisiae, the PHO5 and the PHO8 genes have become a well known system to investigate the role of chromatin structure in transcriptional regulation. Both genes, which encode a nonspecific acid and alkaline phosphatase, respectively, are regulated in response to the phosphate concentration by the same transcription factor, Pho4. Under repressing (+Pi) conditions, PHO5 and PHO8 promoters are assembled into an array of positioned nucleosomes. Upon induction both promoters undergo characteristic chromatin remodeling. Chromatin remodeling at the PHO8 promoter requires the SWI/SNF complex and SAGA at a step subsequent to the binding of the transcription factor Pho4. In the case of PHO5 the chromatin transition also requires the transcription factor Pho4. Still the precise mechanism underlying the alteration in PHO5 chromatin structure is not understood. As aforementioned the remodeling event is dependent on the activation domain of Pho4 and acidic activation domains have been shown to interact with components of the basal transcription machinery as well as with components of transcriptional coactivators including ATP-dependent chromatin-remodeling machines. Since chromatin remodeling is a prerequisite for transcriptional activation rather than the result of active transcription, it is assumed that Pho4 recruits remodeling activities to the PHO5 promoter region prior to the general transcription machinery. Data will be presented demonstrating the role of SWI/SNF in increasing the rate of chromatin remodeling at the PHO5 promoter. In addition, the physical association of SWI/SNF with the promoter region before and after PHO5 and PHO8 induction has been investigated by the ChIP (Chromatin Immunoprecipitation) technology.

chromatin remodeling; yeast PHO5 promoter; transcriptional regulation

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