A Genome-Wide Screen Identifies the Evolutionarily Conserved KEOPS Complex as a Telomere Regulator

Abstract

Telomere capping is the essential function of telomeres. To identify new genes involved in telomere capping, we carried out a genome-wide screen in Saccharomyces cerevisiae for suppressors of cdc13-1, an allele of the telomere-capping protein Cdc13. We report the identification of five novel suppressors, including the previously uncharacterized gene YML036W, which we name CGI121. Cgi121 is part of a conserved protein complex -- the KEOPS complex -- containing the protein kinase Bud32, the putative peptidase Kae1, and the uncharacterized protein Gon7. Deletion of CGI121 suppresses cdc13-1 via the dramatic reduction in ssDNA levels that accumulate in cdc13-1 cgi121 mutants. Deletion of BUD32 or other KEOPS components leads to short telomeres and a failure to add telomeres de novo to DNA double-strand breaks. Our results therefore indicate that the KEOPS complex promotes both telomere uncapping and telomere elongation.

Cell Polarity in Saccharomyces cerevisiae Depends on Proper Localization of the Bud9 Landmark Protein by the EKC/KEOPS Complex

“…The EKC/KEOPS complex consists of Kae1p, Bud32p, Cgi121p, Gon7p, and Pcc1p in haploid cells (Downey et al 2006;Kisseleva-Romanova et al 2006). We investigated whether the EKC/KEOPS complex is involved in bipolar bud-site selection.…”

“…It was also identified as a gene that regulates bud-site selection of diploid cells through a genome-wide analysis (Ni and Snyder 2001). Bud32p is involved in the signaling pathway of Sch9p kinase (Peggion et al 2008) and is also involved in telomere or transcriptional regulation as a component of the EKC/ KEOPS complex (Downey et al 2006;Kisseleva-Romanova et al 2006). In an analysis with gel-filtration chromatography in haploid cells, the subcomplex containing only Kae1p and Bud32p was observed in yeast cells although it could have been a preparation artifact (Kisseleva-Romanova et al 2006).…”

“…BUD32 was originally found as a gene encoding an atypical protein kinase that belongs to the piD261 family of atypical Ser/Thr protein kinases found in virtually all eukaryotic and archaeal organisms (Stocchetto et al 1997). Recently, two independent studies of haploid cells have shown that Bud32p is a component of the KEOPS (kinase, putative endopeptidase, and other proteins of small size) or the EKC (endopeptidase-like, kinase, chromatinassociated) complexes with functions of telomere maintenance and transcriptional regulation, respectively (Downey et al 2006;Kisseleva-Romanova et al 2006). Cgi121p, a component of the KEOPS complex, was identified by a genome-wide screen as a suppressor of cdc13-1, an allele of the gene encoding the telomere-capping protein Cdc13p (Downey et al 2006).…”

“…The components of the KEOPS complex containing Cgi121p are the protein kinase Bud32p, the putative peptidase Kae1p, and the uncharacterized protein Gon7p. Deletion of BUD32 or genes encoding other KEOPS components produced phenotypes with short telomeres and failed to synthesize de novo telomeres to DNA doublestranded breaks (Downey et al 2006). The EKC complex contains a homolog of cancer-testis antigens (Pcc1p) and four additional proteins found in the KEOPS complex.…”

“…Recently, two independent studies of haploid cells have shown that Bud32p is a component of the KEOPS (kinase, putative endopeptidase, and other proteins of small size) or the EKC (endopeptidase-like, kinase, chromatinassociated) complexes with functions of telomere maintenance and transcriptional regulation, respectively (Downey et al 2006;Kisseleva-Romanova et al 2006). Cgi121p, a component of the KEOPS complex, was identified by a genome-wide screen as a suppressor of cdc13-1, an allele of the gene encoding the telomere-capping protein Cdc13p (Downey et al 2006). The components of the KEOPS complex containing Cgi121p are the protein kinase Bud32p, the putative peptidase Kae1p, and the uncharacterized protein Gon7p.…”