RRS1, a conserved essential gene, encodes a novel regulatory protein required for ribosome biogenesis in Saccharomyces cerevisiae

A secretory defect causes specific and significant transcriptional repression of both ribosomal protein and rRNA genes (K, Mizuta and J. R. Warner, Mel. Cell. Biol, 14:2493-2502, 1993), suggesting the coupling of plasma membrane and ribosome syntheses. In order to elucidate the molecular mechanism of the signaling pathway, we isolated a cold-sensitive mutant with a mutation in a gene termed RRS1 (regulator of ribosome synthesis), which appeared to be defective in the signaling pathway, The rrs1-1 mutation greatly reduced transcriptional repression of both rRNA and ribosomal protein genes that is caused by a secretory defect. RRS1 is a novel, essential gene encoding a nuclear protein of 203 amino acid residues that is conserved in eukaryotes, A conditional rrs1-null mutant was constructed by placing RRS1 under the control of the GAL1 promoter, Rrs1p depletion caused defects in processing of pre-rRNA and assembly of ribosomal subunits.