A long noncoding (lnc)RNA governs expression of the phosphate transporter Pho84 in fission yeast and has cascading effects on the flanking  prt  lncRNA and  pho1  genes.
The expression of the phosphate transporter Pho84 in fission yeast  Schizosaccharomyces pombe  is repressed in phosphate-rich medium and induced during phosphate starvation. Two other phosphate-responsive genes in  S. pombe  ( pho1  and  tgp1 ) had been shown to be repressed in  cis  by transcription of a long noncoding (lnc) RNA from the upstream flanking gene, but whether  pho84  expression is regulated in this manner is unclear. Here, we show that repression of  pho84  is enforced by transcription of the SPBC8E4.02c locus upstream of  pho84  to produce a lncRNA that we name  prt2  (   p ho - r epressive  t ranscript 2). We identify two essential elements of the  prt2  promoter, a HomolD box and a TATA box, mutations of which inactivate the  prt2  promoter and de-repress the downstream  pho84  promoter under phosphate-replete conditions. We find that  prt2  promoter inactivation also elicits a cascade effect on the adjacent downstream  prt  (lncRNA) and  pho1  (acid phosphatase) genes, whereby increased  pho84  transcription down-regulates  prt  lncRNA transcription and thereby de-represses  pho1  Our results establish a unified model for the repressive arm of fission yeast phosphate homeostasis, in which transcription of  prt2 ,  prt , and  nc-tgp1  lncRNAs interferes with the promoters of the flanking  pho84 ,  pho1 , and  tgp1  genes, respectively.
Garg A, Sanchez AM, Shuman S, Schwer B