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Multicopy Suppressor (multicopy + suppressor)
Selected AbstractsHigh dosage Rhp51 suppression of the MMS sensitivity of DNA structure checkpoint mutants reveals a relationship between Crb2 and Rhp51GENES TO CELLS, Issue 7 2003Monique F.M.A. Smeets Background: In eukaryotic cells DNA structure checkpoints organize the cellular responses of DNA repair and transient cell cycle arrest and thereby ensure genomic stability. To investigate the exact role of crb2+ in the DNA damage checkpoint response, a genetic screen was carried out in order to identify suppressors of the conditional MMS sensitivity of a crb2-1 mutant. Here we report the isolation of rhp51+ as a multicopy suppressor. Results: We show that suppression is not specific for the checkpoint mutant while it is specific for the MMS treatment. Rescue by rhp51+ over-expression is not a consequence of increased recombination repair or checkpoint compensation and epistasis analysis confirms that crb2+ and rhp51+ function in different pathways. A tight linkage between the two pathways is nevertheless suggested by the complementary expression or modification of Crb2 and Rhp51 proteins. Crb2 protein stability is down-regulated when Rhp51 is over-expressed and up-regulated in the absence of Rhp51. The up-regulation of Crb2 is independent of the activation of DNA structure checkpoints. Conversely Rhp51 is more readily activated and differentially modified in the absence of Crb2 or other checkpoint proteins. Conclusions: We conclude that fission yeast Crb2 and Rhp51 function in two parallel, tightly connected and coordinately regulated pathways. [source] Yeast Saccharomyces cerevisiae has two cis -prenyltransferases with different properties and localizations.GENES TO CELLS, Issue 6 2001Implication for their distinct physiological roles in dolichol synthesis Background Dolichol is a family of long-chain polyprenols, which is utilized as a sugar carrier in protein glycosylation in the endoplasmic reticulum (ER). We have identified a key enzyme of the dolichol synthesis, cis -prenyltransferase, as Rer2p from Saccharomyces cerevisiae. We have also isolated a multicopy suppressor of an rer2 mutant and named it SRT1. It encodes a protein similar to Rer2p but its function has not been established. Results The cis -prenyltransferase activity of Srt1p has been proved biochemically in the lysate of yeast cells lacking Rer2p. The polyprenol product of Srt1p is longer in chain length than that of Rer2p and is not sufficiently converted to dolichol and dolichyl phosphate, unlike that of Rer2p. The subcellular localization of these two isozymes has been examined by immunofluorescence microscopy and by the use of GFP fusion proteins. Whereas GFP-Rer2p is localized to the continuous ER and some dots associated with the ER, GFP-Srt1p shows only punctate localization patterns. Immunofluorescence double staining with Erg6p, a marker of lipid particles in yeast, indicates that Srt1p is mainly localized to lipid particles (lipid bodies). RER2 is mainly expressed in the early logarithmic phase, while the expression of SRT1 is induced in the stationary phase. Conclusions We have shown that yeast has two active cis -prenyltransferases with different properties. This result implies that the two isozymes have different physiological roles during the life cycle of the yeast. [source] Novel DNA binding protein SarZ contributes to virulence in Staphylococcus aureusMOLECULAR MICROBIOLOGY, Issue 6 2006Chikara Kaito Summary We previously reported that the cvfA gene is a virulence regulatory gene in Staphylococcus aureus. Here, we identified a novel gene named sarZ that acts as a multicopy suppressor of decreased haemolysin production in the cvfA deletion mutant. The amount of sarZ transcripts was decreased in the cvfA mutant. The sarZ -deletion mutant produced less haemolysin and attenuated virulence in a silkworm-infection model and a mouse-infection model. The amino acid sequence of the sarZ gene product had 19% identity with the transcription factor MarR in Escherichia coli, and the internal region contained a winged helix,turn,helix motif (wHTH), a known DNA binding domain. Purified recombinant SarZ protein had binding affinity for the promoter region of the hla gene that encodes ,-haemolysin. SarZ mutant proteins with an amino acid substitution in the N-terminal region or in the wHTH motif had significantly decreased DNA binding. The mutated sarZ genes encoding SarZ mutant proteins with a low affinity for DNA did not complement the decreased haemolysin production or the attenuated killing ability against silkworms in the sarZ mutant. These results suggest that the DNA binding activity of the SarZ protein is required for virulence in S. aureus. [source] The bromodomain-containing protein Bdf1p acts as a phenotypic and transcriptional multicopy suppressor of YAF9 deletion in yeastMOLECULAR MICROBIOLOGY, Issue 3 2004Michele M. Bianchi Summary It was observed previously that the deletion of the open reading frame YNL107w (YAF9) was highly pleiotropic in yeast and caused defective growth phenotypes in the presence of several unrelated inhibitors, including caesium chloride. We have selected multicopy extragenic suppressor genes, revealing that this phenotype can be suppressed by overdosing the transcription factors BDF1 and GAT1 in the yaf9, strain. We focused our analysis on suppression by BDF1 and performed a genome-wide transcript analysis on a yaf9, strain, compared with the wild-type and BDF1 -suppressed strains. YAF9 deletion has a clear effect on transcription and leads to modulation of the level of expression of several genes. Transcription of a considerable portion of the underexpressed genes is restored to wild-type levels in the BDF1 -suppressed strain. We show by chromatin immunoprecipitation that both Yaf9p and Bdf1p bind to promoters of some of these genes and that the level of H3 and H4 acetylation at one of these promoters is significantly lowered in the yaf9 deleted strain, compared with the wild-type and the BDF1 -suppressed strains. [source] Overexpression of Upf1p compensates for mitochondrial splicing deficiency independently of its role in mRNA surveillanceMOLECULAR MICROBIOLOGY, Issue 4 2004B. De Pinto Summary In yeast the UPF1, UPF2 and UPF3 genes encode three interacting factors involved in translation termination and nonsense-mediated mRNA decay (NMD). UPF1 plays a central role in both processes. In addition, UPF1 was originally isolated as a multicopy suppressor of mitochondrial splicing deficiency, and its deletion leads to an impairment in respiratory growth. Here, we provide evidence that inactivation of UPF2 or ,UPF3, ,like ,that ,of ,UPF1, ,leads ,to ,an ,impairment in respiratory competence, suggesting that their products, Upf1p, Upf2p and Upf3p, are equivalently involved in mitochondrial biogenesis. In addition, however, we show that only Upf1p acts as a multicopy suppressor of mitochondrial splicing deficiency, and its activity does not require either Upf2p or Upf3p. Mutations in the conserved cysteine- and histidine-rich regions and ATPase and helicase motifs of Upf1p separate the ability of Upf1p to complement the respiratory impairment of a ,upf1 strain from its ability to act as a multicopy suppressor of mitochondrial splicing deficiency, indicating that distinct pathways express these phenotypes. In addition, we show that, when overexpressed, Upf1p is not detected within mitochondria, suggesting that its role as multicopy suppressor of mitochondrial splicing deficiency is indirect. Furthermore, we provide evidence that cells overexpressing certain upf1 alleles accumulate a phosphorylated isoform of Upf1p. Altogether, these results indicate that overexpression of Upf1p compensates for mitochondrial splicing deficiency independently of its role in mRNA surveillance, which relies on Upf1p,Upf2p,Upf3p functional interplay. [source] | ||||||||||