Gtr1‐Gtr2, Ego1‐Ego3 and Vam6‐independent cytoplasmic Gln3 sequestration in conditions of nitrogen excess (609.17)

Abstract

The Gtr1/2, Ego1/3 complexes and Vam6 have been reported to be required for TorC1 kinase activation. In turn, activated TorC1 is accepted to be required for cytoplasmic Gln3 sequestration based on the observations that: (i) a Tor1‐Gln3 interaction is required for high level cytoplasmic Gln3 sequestration in nitrogen excess and (ii) rapamycin treatment elicits cytoplasmic to nuclear Gln3 relocation. These correlations lead to the a priori prediction that Gtr1/2, Ego1/3 and Vam6 should also be similarly required for downstream cytoplasmic Gln3 sequestration when cells are cultured in excess nitrogen. To test this hypothesis, we individually deleted the genes encoding each of the above proteins and determined whether the Gtr‐Ego complexes were required for cytoplasmic Gln3 sequestration in nitrogen rich medium. In every case cytoplasmic Gln3 sequestration occurred to the same degree in the deletion mutants as in wild type. These data indicate that either cytoplasmic Gln3 sequestration occurs in response to a TorC1‐independent regulatory pathway and/or alternatively that TorC1 activation can occur via both Gtr1/2‐Ego1/3‐Vam6‐dependent and ‐independent regulatory pathways.Grant Funding Source: NIH GM‐35642; FRFC 2.4547.11