engleski

Role of non-coding RNAs in transcriptional regulation of yeast Saccharomyces cerevisiae PHO genes

Promoters of yeast Saccharomyces cerevisiae PHO genes are a classical model system for studying promoter regulation through chromatin remodeling (1). Upon induction, chromatin structure at these promoters undergoes a massive transition, which requires action of a large network of chromatin modifiers and remodelers. Interestingly, strand-specific tilling array data revealed that these loci also exhibit transcription of non-coding RNAs (ncRNAs), which have no coding capacity but have potential regulatory roles (2). We are now exploring the role of non-coding transcription in regulation of PHO5 and PHO8 gene expression, by using a mutant context in which rapid degradation of ncRNAs is abolished by interfering with the activity of RNA exosome complex, that normally eliminates them. We found that depletion of the nuclear-specific catalytic exosome subunit Rrp6 leads to delayed transcriptional activation of PHO genes under inducing conditions. This is caused by a delay at the level of promoter chromatin remodeling, since both promoters show less accessibility to cleavage by restriction endonucleases during early hours of induction in rrp6 cells compared to wild type cells. We further demonstrate that, at the PHO5 gene, this negative effect on transcriptional activation rate is not an indirect consequence of impaired signal transduction in rrp6 cells and that exchanging the native ORF with lacZ ORF restores transcriptional activation kinetics of PHO5 promoter to wild type level, which implies that an antisense RNA transcribed across the PHO5 ORF and through the promoter (3) is the most likely candidate for the regulatory non-coding transcript at this locus. The focus of future experiments will be discovering the molecular mechanism through which ncRNAs act at yeast PHO genes to finely tune their expression level. 1. Korber & Barbarić. NAR. 42:17, 10888-10902. (2014) 2. Lardenois et al. PNAS 108: 3, 1058-1063. (2011) 3. Uhler et al. PNAS. 104:19, 8011-8016. (2007)

PHO5 ; RNA exosome ; non-coding RNA ; antisense RNA

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