UME6 is a key regulator of nitrogen repression and meiotic development.

Abstract

This report describes the identification, cloning, and molecular analysis of UME6 (CAR80/CARGRI), a key transcriptional regulator of early meiotic gene expression. Loss of UME6 function results in the accumulation of fully derepressed levels (70-to 100-fold increase above basal level) of early meiotic transcripts during vegetative growth. In contrast, mutations in five previously identified UME loci (UME1 to UME5), result in low to moderate derepression (2-to 10-fold increase) of early meiotic genes. The behavior of insertion and deletion alleles indicates that UME6 is dispensable for mitotic division but is required for meiosis and spore germination. Despite the high level of meiotic gene expression during vegetative growth, the generation times of ume6 mutant haploid and diploid cells are only slightly reduced. However, both ascus formation and spore viability are affected more severely. The UME6 gene encodes a 91-kD protein that contains a C6 zinc cluster motif similar to the DNA-binding domain of GAL4. The integrity of this domain is required for UME6 function. It has been reported recently that a mutation in CAR80 fails to complement an insertion allele of UME6. CAR80 is a gene required for nitrogen repression of the arginine catabolic enzymes. Here, through sequence analysis, we demonstrate that UME6 and CAR80 are identical. Analyses of UME6 mRNA during both nitrogen starvation and meiotic development indicate that its transcription is constitutive, suggesting that regulation of UME6 activity occurs at a post-transcriptional level.

Ume6 transcription factor is part of a signaling cascade that regulates autophagy

“…To identify candidate transcriptional regulators of ATG8, we analyzed its promoter region and identified an upstream regulatory sequence, URS1, which is a consensus binding site for the transcription factor Ume6 (Fig. 1A), which was previously identified during a whole-genome microarray analysis (9)(10)(11). The URS1 consensus site consists of two invariant GGC repeats, which tend to be immediately preceded by a C and several T nucleotides and followed by a T and two A nucleotides, although some variability exists in these positions (9).…”

The Ume6 regulon coordinates metabolic and meiotic gene expression in yeast

“…Ume6-regulated genes were expected to fall into two major classes: (i) direct target genes, whose promoters are bound by Ume6, and (ii) indirect targets showing altered expression as a result of downstream effects caused by loss of Ume6. To identify the subset of genes that are most likely direct targets of Ume6, the promoters of differentially expressed genes (Ϫ600 to ϩ200 with respect to the ATG start codon) were screened for the presence of the core hexamer URS1 A sequence (5Ј-GGCGGC-3Ј or its reverse complement) bound by Ume6 in vivo and in vitro (2,17).…”

“…Prior studies in our lab and others showed that Ume6 is a major regulator of early meiotic expression (2,10,22,35). Indeed, the present analysis shows that a significant fraction of Ume6 activity is devoted to meiotic functions, because more than half of the known direct Ume6 targets play important roles , metabolism (16%), cell growth͞division͞DNA synthesis (12%), intracellular transport (9.5%), cell rescue͞defense͞aging (8.1%), transcription (8.1%), cellular biogenesis (6.8%), protein destination (6.8%), protein synthesis (6.8%), transport facilitation (4%), ionic homeostasis (2.7%) (40).…”

“…In a ume6⌬ mutant, these genes are derepressed during vegetative growth (exhibiting unscheduled meiotic expression; ref. 2). They also fail to be induced to full levels in meiosis, resulting in an inability to sporulate (10,14).…”

“…UME6 encodes a DNA-binding protein (1,2) that associates with the upstream regulatory sequence URS1 A (consensus 5Ј-TCGGCGGCT-3Ј) to regulate transcription of genes responding to metabolites such as glucose, nitrogen and inositol (3)(4)(5)(6)(7)(8) and, in some cases, with a noncanonical URS1 (URS1 B ; 5Ј-SGWGGMRRNANW-3Ј) to regulate genes involved in DNA repair (9). Although Ume6 is dispensable for growth, it controls efficient mating of haploids and is essential for the initiation and progression of meiosis (2,10). Meiosis in yeast occurs when a͞␣ diploid cells are starved for both nitrogen and a fermentable carbon source (e.g., glucose), culminating in the formation of four haploid spores (reviewed in ref.…”