Recruitment of the ArgR/Mcm1p repressor is stimulated by the activator Gcn4p: a self-checking activation mechanism.
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 to ARG1 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. Mcm1p and Arg80p were found in a soluble complex lacking Arg81p and Arg82p, and both Mcm1p and Arg80p were efficiently recruited to ARG1 in wild-type cells in the presence or absence of exogenous arginine, and also in arg81Delta 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 arginine-regulated repressor, Gcn4p can precisely modulate its activation function at ARG1 according to the availability of arginine.
Yoon
Sungpil
S
Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Govind
Chhabi K
CK
Qiu
Hongfang
H
Kim
Soon-ja
SJ
Dong
Jinsheng
J
Hinnebusch
Alan G
AG
D001120:Arginine / Q000096:biosynthesis / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D025461:Feedback, Physiological; D015966:Gene Expression Regulation, Fungal; D007532:Isoleucine / Q000172:deficiency; D046911:Macromolecular Substances; D026341:Minichromosome Maintenance 1 Protein / Q000378:metabolism* / Q000502:physiology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism / Q000502:physiology; D011485:Protein Binding / Q000502:physiology; D011494:Protein Kinases / Q000378:metabolism / Q000502:physiology*; D012097:Repressor Proteins / Q000378:metabolism* / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology; D014158:Transcription, Genetic; D014633:Valine / Q000172:deficiency
C066955:ARG80 protein, S cerevisiae; C067875:ARG81 protein, S cerevisiae; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D026341:Minichromosome Maintenance 1 Protein; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D007532:Isoleucine; D001120:Arginine; D011494:Protein Kinases; C425775:ARG82 protein, S cerevisiae; D017853:Phosphotransferases (Alcohol Group Acceptor); D014633:Valine