General Amino Acid Control and 14-3-3 Proteins Bmh1/2 Are Required for Nitrogen Catabolite Repression-Sensitive Regulation of Gln3 and Gat1 Localization.

Nitrogen catabolite repression (NCR), the ability of Saccharomyces cerevisiae to use good nitrogen sources in preference to poor ones, derives from nitrogen-responsive regulation of the GATA family transcription activators Gln3 and Gat1 In nitrogen-replete conditions, the GATA factors are cytoplasmic and NCR-sensitive transcription minimal. When only poor nitrogen sources are available, Gln3 is nuclear, dramatically increasing GATA factor-mediated transcription. This regulation was originally attributed to mechanistic Tor protein kinase complex 1 (mTorC1)-mediated control of Gln3 However, we recently showed that two regulatory systems act cumulatively to maintain cytoplasmic Gln3 sequestration, only one of which is mTorC1.