Transcription factor that mediates regulation of both acid- and alkaline-expressed genes in response to ambient pH. At alkaline ambient pH, activates transcription of alkaline-expressed genes (including RIM101 itself), mainly by repressing transcriptional repressors of those genes, and represses transcription of acid-expressed genes. Required for meiosis, sporulation and invasive growth. Binds to DNA. Interacts with RIM20, which probably binds to the two YPX[LI] motifs and is required for proteolytic processing. Activated by C-terminal proteolytic cleavage. At neutral to alkaline ambient pH, the signaling protease (probably RIM13) cleaves RIM101, removing a C-terminal 8 kDa peptide to yield the active form. Present with 1822 molecules/cell in log phase SD medium. Belongs to the pacC/RIM101 family.