Transcription factor that activates genes required for degradation of extracellular protein and uptake of peptides such as the secreted aspartyl protease SAP2 or the oligopeptide transporter OPT1. Required for virulence. Synthesized as latent cytoplasmic precursor, which, upon a signal initiated by the plasma membrane SPS amino acid sensor system (including CSY1 and CSH3), becomes proteolytically activated and relocates to the nucleus, where it induces the expression of SPS-sensor-regulated genes. Localizes to the cytoplasm in its unprocessed form and is targeted to the nucleus after proteolytic processing upon induction by amino acids. Expression is down-regulated in presence of extracellular amino acids. Activated by the amino acid-induced proteolytic removal of an N-terminal inhibitory domain. Impairs expression of SAP2 and OPT1. Impairs virulence in Drosophila as a host model.