| Popis: |
RNA-sequencing studies discovered pervasive transcription across eukaryotic genomes leading to the transcription of numerous non-coding RNAs (ncRNAs). ncRNAs have been shown to be important regulators of gene expression, acting via modulation of chromatin structure, promoter interference and/or over-lapping sense/antisense pairs. ThePHO5gene encodes secreted nonspecific acid phosphatase, which is located in the periplasmic space of the cell and plays a role in phosphate metabolism. Accordingly, PHO5 expression is regulated in response to phosphate concentration in the cell via the PHO signaling pathway, so that it is suppressed when intracellular concentration is abundant and induced under conditions of phosphate deficiency. This regulation is primarily achieved through phosphorylation of the major activator Pho4. At high phosphate concentrations, Pho4 is phosphorylated by the cyclin-dependent-kinase (Pho80-Pho85), accumulates in the nucleus, and activates transcription of the PHO5 gene. Another level of complexity of PHO5 promoter regulation was revealed by mapping the PHO5 antisense transcript, CUT025. This transcript initiates from the 3’ region of PHO5 ORF and extends across the promoter region with a size of 2.4 kb. It is produced only in cells growing under repressive (phosphate-rich) conditions and is more abundant in rrp6D mutant than in wild-type cells, indicating its degradation by the nuclear RNA exosome. In this work, we examined the effects of noncoding antisense transcription on PHO5 gene expression by enhancing or impairing elongation of the PHO5 antisense transcript. In both cases, our results demonstrate that antisense transcription has a negative effect on PHO5 gene transcription. Furthermore, we provide evidence that this negative effect occurs through a chromatin based mechanism mediated by antisense transcription that reduces the accessibility of chromatin structure at the PHO5 gene promoter. |
