Regulatory circuit for responses of nitrogen catabolic gene expression to the GLN3 and DAL80 proteins and nitrogen catabolite repression in Saccharomyces cerevisiae

Abstract

We demonstrate that expression of the UGA1, CAN1, GAP1, PUT1, PUT2, PUT4, and DAL4 genes is sensitive to nitrogen catabolite repression. The expression of all these genes, with the exception of UGA1 and PUT2, also required a functional GLN3 protein. In addition, GLN3 protein was required for expression of the DAL1, DAL2, DAL7, GDH1, and GDH2 genes. The UGA1, CAN1, GAP1, and DAL4 genes markedly increased their expression when the DAL80 locus, encoding a negative regulatory element, was disrupted. Expression of the GDH1, PUT1, PUT2, and PUT4 genes also responded to DAL80 disruption, but much more modestly. Expression of GLN1 and GDH2 exhibited parallel responses to the provision of asparagine and glutamine as nitrogen sources but did not follow the regulatory responses noted above for the nitrogen catabolic genes such as DAL5. Steady-state mRNA levels of both genes did not significantly decrease when glutamine was provided as nitrogen source but were lowered by the provision of asparagine. They also did not respond to disruption of DAL80.

Gzf3p, a fourth GATA factor involved in nitrogen‐regulated transcription in Saccharomyces cerevisiae

“…These results suggest that the extent of Uga43p-mediated inhibition of Nillp is gene specific. This conclusion is consistent with the previous observation that deletion of UGA43 leads to variable degrees of derepression of nitrogen-regulated genes (Daugherty et a/., 1993). In NH4+-grown gln3A cells, further lack of Gzf3p causes partial derepression of reporter gene expression (Table 5 , column 2, lines 2 and 3), confirming the role of Gzf3p in nitrogen repression of Nill p-dependent transcription.…”

“…The GATA factor encoded by the UGA431 DALBO gene (Cunningham and Cooper, 1991 ;Coornaert et a/., 1992) was isolated because mutations in this gene cause constitutive expression of inducible genes involved in allantoin (Chilsholm and Cooper, 1982) or y-aminobutyrate (Vissers et a/., 1989) utilization. This GATA factor downregulates to varying degrees the expression of most tested nitrogen-sensitive genes (Daugherty et a/., 1993). In vitro, Uga43plDa180p binds to specific arrangements of 5'-GATA-3' core sequences (Cunningham et a/., 1994).…”

Gln3p Nuclear Localization and Interaction with Ure2p inSaccharomyces cerevisiae

“…Total RNA was prepared (11), and hybridization reactions were performed as described (11). Hybridization probes were generated using PCR products (7).…”

“…In yeast, the GATA family proteins Gln3p, Gat1p/Nil1p, Dal80p, Deh1p/Gzf3p have been studied as the main regulators of nitrogen catabolic gene expression (4-6), and recently their regulatory functions also been shown to be far more diverse (7,8). Gln3p and Gat1p are transcriptional activators, whereas Dal80p and Deh1p repress transcription by competing with these activators for binding to their target GATA sequences (4)(5)(6)(9)(10)(11) …”

Constitutive and Nitrogen Catabolite Repression-sensitive Production of Gat1 Isoforms

“…However, detailed genetic analyses using single, double, and triple gln3, dal80 (a GATA family repressor), and ure2 mutants led to the demonstration that NCR-sensitive transcription could be activated not only by Gln3, but also by another unknown transcription factor whose production and operation were themselves NCR-sensitive, Gln3-dependent, and Dal80-and Ure2-regulated (11)(12)(13)(14). The transcription factor whose existence was predicted in that early work was subsequently cloned and designated GAT1/NIL1 (15,16).…”