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Transcription of the arginine biosynthetic gene ARG1 is repressed by the ArgR/Mcm1p complex in arginine-replete cells and activated by Gcn4p, a transcription factor induced by starvation for any amino acid. We show that all four subunits of the arginine repressor are recruited toARG1 by Gcn4p in cells replete with arginine but starved for isoleucine/valine. None of these proteins is recruited to the Gcn4p target genes ARG4 and SNZ1, which are not regulated by ArgR/Mcm1p. Mcmlp and Arg80p were found in a soluble complex lacking Arg81p and ArgS2p, and both Mcmlp and Arg80p were efficiently recruited toARG1 in wild-type cells in the presence or absence of exogenous arginine, and also in arg81A cells. By contrast, the recruitment of Arg81p and Arg82p was stimulated by exogenous arginine. These findings suggest that Gcn4p constitutively recruits an Mcm1p/Arg80p heterodimer and that efficient assembly of a functional repressor also containing Arg81p and Arg82p occurs only in arginine excess. By recruiting an arginineregulated repressor, Gcn4p can precisely modulate its activation function at ARG1 according to the availability of arginine. [ABSTRACT FROM AUTHOR]