Phosphoinositide [PI(3,5)P₂] lipid-dependent regulation of the general transcriptional regulator Tup1

Abstract

Transcriptional activity of a gene is governed by transcriptional regulatory complexes that assemble/disassemble on the gene and control the chromatin architecture. How cytoplasmic components influence the assembly/ disassembly of transcriptional regulatory complexes is poorly understood. Here we report that the budding yeast Saccharomyces cerevisiae has a chromatin architecture-modulating mechanism that is dependent on the endosomal lipid PI(3,5)P 2 . We identified Tup1 and Cti6 as new, highly specific PI(3,5)P 2 interactors. Tup1-which associates with multiple transcriptional regulators, including the HDAC (histone deacetylase) and SAGA complexes-plays a crucial role in determining an activated or repressed chromatin state of numerous genes, including GAL1. We show that, in the context that the Gal4 activation pathway is compromised, PI(3,5)P 2 plays an essential role in converting the Tup1-driven repressed chromatin structure into a SAGA-containing activated chromatin structure at the GAL1 promoter. Biochemical and cell biological experiments suggest that PI(3,5)P 2 recruits Cti6 and the Cyc8-Tup1 corepressor complex to the late endosomal/vacuolar membrane and mediates the assembly of a Cti6-Cyc8-Tup1 coactivator complex that functions to recruit the SAGA complex to the GAL1 promoter. Our findings provide important insights toward understanding how the chromatin architecture and epigenetic status of a gene are regulated by cytoplasmic components.[Keywords: PI(3,5)P 2 lipid; Cti6-Cyc8-Tup1; GAL1 transcriptional induction; lysosomal vacuolar endosome]

Lysosome enlargement during inhibition of the lipid kinase PIKfyve proceeds through lysosome coalescence

“…These observations are consistent with Wang et al and Krishna et al who also showed that mTORC1 retains its activity in PIKfyve-abrogated cells (Wang et al, 2015;Krishna et al, 2016). We considered the possibility that mTORC1 and starvation controls PIKfyve activity instead, which may then modulate TFEB, perhaps by a PtdIns(3,5)P 2 -dependent localization of TFEB to lysosomes, as has been shown for Tup1, a transcription factor in yeast that controls galactose metabolism (Han and Emr, 2011). Yet, we could not observe a significant decrease in PtdIns(3,5)P 2 levels in mTOR-inhibited cells, though we cannot exclude disruption of a specific pool of PtdIns(3,5)P 2 or of PtdIns(5)P, a lipid that is directly or indirectly synthesized by PIKfyve (Zolov et al, 2012;Sbrissa et al, 2012).…”

The Filamentous Growth MAPK Pathway Responds to Glucose Starvation Through the Mig1/2 Transcriptional Repressors in Saccharomyces cerevisiae

“…and associate with internal membranes, resulting in modification of its gene expression function (Han and Emr 2011). It is possible that Mig1 and Mig2 are modified in some way by associating with Msb2, Opy2, Ste7, or Kss1, which results in alteration of their normal function.…”

The Phosphatidylinositol 3,5-Bisphosphate (PI(3,5)P2)-dependent Tup1 Conversion (PIPTC) Regulates Metabolic Reprogramming from Glycolysis to Gluconeogenesis

“…Our previous study on the yeast galactose metabolism gene, GAL1, identified a novel phosphatidylinositol 3,5-bisphosphate (PI(3,5)P 2 ) 2 -dependent transcriptional regulatory mechanism (12). PI(3,5)P 2 is a phosphoinositide lipid that is synthesized from phosphatidylinositol 3-phosphate by the Fab1 phosphatidylinositol-3-phosphate 5-kinase at the late endosomal/vacuolar lysosomal membranes (13,14).…”