Yeast PKA catalytic subunits localize on stress and processing foci under heat stress.

IRINA MARCOVICH; VANESA TUDISCA; PAULA PORTELA

Mendoza, Argentina

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.; 2012

SAIB

Various stresses cause a fast and transient redistribution of nontranslated mRNAs into SGs (stress granules) and processing granules (PBs) in response to environmental injuries. In Saccharomyces cerevisiae, sphingolipids mediate the formation of PBs during heat stress. PKA regulatory subunit is encoded by the BCY1 gene, and the catalytic subunits are encoded by three genes: TPK1, TPK2 and TPK3. Here we report that during middle heat stress (37ºC) Tpk2‐GFP re‐localizes to the cytoplasm while Tpk1 and Tpk3 require severe heat stress (46ºC) for relocalization. Bcy1 shows an unresponsive nucleo‐cytoplasmic distribution at both temperatures. In addition, at 37ºC only Tpk3 shows foci accumulation whereas at 46ºC Tpk2 also accumulates in foci. Inhibition of the synthesis of sphingolipids previous to heat stress impairs the Tpk cytoplasmic re‐localization and reduces Tpk2 and Tpk3 foci accumulation, suggesting sphingolipid‐dependent pathway is involved in Tpk localization. Co‐localization experiments in cells expressing Tpk2‐GFP or Tpk3‐GFP and Dcp1‐RFP (PBs marker) or Rpg1‐RFP (SGs marker) during heat stress revealed that Tpk2 and Tpk3 are associated with PBs and SGs. We have previously described that unstressed tpk3Δ strain contains foci that resemble SG induced by heat shock. Here we show that SG granules accumulated by TPK3 deletion have a protective function against heat stress injury.