Inorganic polyphosphate abets silencing of a sub-telomeric gene cluster in fission yeast

Inorganic polyphosphate (PolyP) is a ubiquitous polymer that plays sundry roles in cell and organismal physiology. Whereas there is evidence for polyphosphate in the cell nucleus, it is unclear whether and how physiological levels of PolyP impact transcriptional regulation in eukarya. To address this issue, we performed transcriptional profiling of fission yeast vtc4{Delta} cells, which lack the catalytic subunit of the Vtc4/Vtc2 polyphosphate polymerase complex and thus have no detectable intracellular PolyP. Deleting Vtc4 elicited the de-repression of four protein-coding genes - SPAC186.04c, gdt1/SPAC186.05, SPAC186.06, and SPAC750.01 - located within a sub-telomeric region of the right arm of chromosome I that is known to be transcriptionally silenced by the TORC2 complex. These sub-telomeric genes were equally de-repressed in vtc2{Delta} cells and in cells expressing polymerase-dead Vtc4, signifying that PolyP synthesis is necessary to abet TORC2-dependent locus-specific gene silencing.