Yeast homolog of a cancer-testis antigen defines a new transcription complex

Abstract

We have isolated a new yeast gene (PCC1) that codes for a factor homologous to human cancer-testis antigens. We provide evidence that Pcc1p is a new transcription factor and that its mutation affects expression of several genes, some of which are involved in cell cycle progression and polarized growth. Mutation of Pcc1p also affects the expression of GAL genes by impairing the recruitment of the SAGA and Mediator co-activators. We characterize a new complex that contains Pcc1p, a kinase, Bud32p, a putative endopeptidase, Kae1p and two additional proteins encoded by ORFs YJL184w and YMLO36w. Genetic and physical interactions among these proteins strongly suggest that this complex is a functional unit. Chromatin immunoprecipitation experiments and multiple genetic interactions of pcc1 mutants with mutants of the transcription apparatus and chromatin modifying enzymes underscore the direct role of the complex in transcription. Functional complementation experiments indicate that the transcriptional function of this set of genes is conserved throughout evolution. The EMBO Journal (2006) IntroductionTranscription of approximately 10% of the yeast genome occurs in a cell-cycle-dependent manner (Spellman et al, 1998). For almost half of these genes, the peak of transcription takes place around START (Spellman et al, 1998;Horak et al, 2002) when cells enter a new cycle and start budding. Thus, it is not surprising that an efficient transcriptional machinery is required for the passage through START. Indeed, mutation of several factors of the transcriptional apparatus leads to defects in START and the accumulation of unbudded cells (Jahng et al, 1988;Prendergast et al, 1990;Drebot et al, 1993;Walker et al, 1997;Koch et al, 1999). Modulation of gene expression is also critical for yeast conjugation. The response to mating pheromone in Saccharomyces cerevisiae involves the transcriptional activation of roughly 200 genes (Roberts et al, 2000), which ultimately determines cell-cycle arrest in the G1 phase and the formation of mating projections.Transcription starts when specific activators bind to their cognate sites on the DNA and recruit co-activator complexes. Co-activators promote the formation of the preinitiation complex (PIC) containing general transcription factors (GTFs) and RNA polymerase II (RNAPII) at the core promoters. This event determines the initiation of transcription, which is followed by elongation and termination.Transcription through chromatin requires the action of chromatin modifying and chromatin remodeling factors. Covalent modifications of histones include phosphorylation, ubiquitylation, methylation and acetylation (Strahl and Allis, 2000;Jenuwein and Allis, 2001). Acetylation of histone N-terminal tails is generally associated with transcriptional activity and histone acetyltransferases (HAT) are recruited to promoters by transcriptional activators. Although several histone deacetylases (HDAC) contribute to transcriptional repression by interacting with specific DNA-binding repressors, recent ...

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 EKC complex contains a homolog of cancer-testis antigens (Pcc1p) and four additional proteins found in the KEOPS complex. Pcc1p is a transcription factor, and its deletion affects the expression of several genes regulated by a-factor and galactose (Kisseleva-Romanova et al 2006). Bud32p is phosphorylated by Sch9p kinase, a yeast member of the Akt/PKB subfamily.…”

L’intrusion des régulateurs de l’épigénome mâle dans les cellules somatiques cancéreuses

“…Cette protéine, PCC1, code pour un facteur de transcription capable de réguler l'expression d'un réseau de gènes impliqué dans le cycle cellulaire et la croissance polarisée chez la levure. Chez les mammifères, ces gènes sont uniquement exprimés dans les cellules germinales et leur dérépression aberrante pourrait affecter égale-ment des réseaux de gènes codant, comme chez la levure, pour des régulateurs cellulaires critiques [24]. De manière intéressante, une kinase normalement exprimée dans les cellules germinales, PBK/TOPK, a été trouvée fréquemment dérégulée dans les cancers du sein.…”