Transcription factor involved in the regulation of gene expression in response to extracellular amino acid levels. Synthesized as latent cytoplasmic precursor, which, upon a signal initiated by the plasma membrane SPS (SSY1-PTR3-SSY5) amino acid sensor system, becomes proteolytically activated and relocates to the nucleus, where it induces the expression of SPS-sensor-regulated genes, including the amino-acid permeases BAP2 and BAP3. Binding to promoters is facilitated by DAL81 (By similarity). Involved in the repression of genes subject to nitrogen catabolite repression and genes involved in stress response. Negatively regulated by inner nuclear membrane proteins ASI1, ASI2 and ASI3, which prevent unprocessed precursor forms that escape cytoplasmic anchoring from inducing SPS-sensor-regulated genes. Interacts (via Region II) with SSY5; protease component of the SPS-sensor. Localizes to the cytoplasm in its unprocessed form and is targeted to the nucleus after proteolytic processing upon induction by amino acids. The N-terminal inhibitory domain contains conserved sequence elements important for cytoplasmic retention (Region I) and proteolytic processing (Region II) of the protein (By similarity). Region I is also required for ASI1/2/3-mediated negative regulation of transcription. Activated by the amino acid-induced proteolytic removal of an N-terminal inhibitory domain by serine protease SSY5, an intrinsic component of the SPS-sensor. Processing requires at least 2 components of the SCF(GRR1) ubiquitin ligase complex, namely the F-box protein GRR1 and the E2 enzyme CDC34, but does not depend on the proteasome. Processing is negatively regulated by the protein phosphatase 2A regulatory subunit RTS1 (By similarity). Present with 6490 molecules/cell in log phase SD medium.