Inviability of a DNA2 deletion mutant is due to the DNA damage checkpoint

Dna2 is a dual polarity exo/endonuclease, and 5' to 3' DNA helicase involved in Okazaki Fragment Processing (OFP) and Double-Strand Break (DSB) Repair. In yeast, DNA2 is an essential gene, as expected for a DNA replication protein. Suppression of the lethality of dna2Δ mutants has been found to occur by two mechanisms: overexpression of RAD27^(scFEN1), encoding a 5' to 3' exo/endo nuclease that processes Okazaki fragments (OFs) for ligation, or deletion of PIF1, a 5' to 3' helicase involved in mitochondrial recombination, telomerase inhibition and OFP. Mapping of a novel, spontaneously arising suppressor of dna2Δ now reveals that mutation of rad9 and double mutation of rad9 mrc1 can also suppress the lethality of dna2Δ mutants. Interaction of dna2Δ and DNA damage checkpoint mutations provides insight as to why dna2Δ is lethal but rad27Δ is not, even though evidence shows that Rad27^(ScFEN1) processes most of the Okazaki fragments, while Dna2 processes only a subset

Use of cancer-specific yeast-secreted in vivo biotinylated recombinant antibodies for serum biomarker discovery

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A NEW GENE AFFECTING THE EFFICIENCY OF MATING-TYPE INTERCONVERSIONS IN HOMOTHALLIC STRAINS OF <i>SACCHAROMYCES CEREVISIAE</i>

ABSTRACT Homothallic strains of Saccharomyes cerevisiae are able to switch efficiently from one mating genotype to another. From a single haploid spore arise both a and α mating type cells, which then self-mate to produce a colony consisting almost exclusively of nonmating a/α diploid cells. We have isolated a mutant homothallic strain that gives rise to colonies that show bisexual mating behavior. The mating reaction is always asymmetric, that is, in some colonies a mating is much stronger than α mating, while others show greater α than a mating.—This mating phenotype arises from the presence of three cell types in a colony: some a/α nonmating diploids and an unequal number of a and α haploid cells. The predominant haploid type is that of the original cell that gives rise to the colony. This mixture of cell types arises from a very reduced efficiency of homothallic mating-type interconversions in the mutant strain.—The mutation, designated switch (swi1-1), behaves as a single genetic locus. The mutation is centromere linked, but not linked to the mating type locus or to any of the homothallism genes: HO, HM  a and HMα. The switch mutation does not affect the efficiency of self-mating, but rather directly affects the frequency of interconversion of mating types.</jats:p

Mating in <i>Saccharomyces cerevisiae:</i> The Role of the Pheromone Signal Transduction Pathway in the Chemotropic Response to Pheromone

Abstract The mating process in yeast has two distinct aspects. One is the induction and activation of proteins required for cell fusion in response to a pheromone signal; the other is chemotropism, i.e., detection of a pheromone gradient and construction of a fusion site available to the signaling cell. To determine whether components of the signal transduction pathway necessary for transcriptional activation also play a role in chemotropism, we examined strains with null mutations in components of the signal transduction pathway for diploid formation, prezygote formation and the chemotropic process of mating partner discrimination when transcription was induced downstream of the mutation. Cells mutant for components of the mitogen-activated protein (MAP) kinase cascade (ste5, ste20, ste11, ste7 or fus3 kss1) formed diploids at a frequency 1% that of the wild-type control, but formed prezygotes as efficiently as the wild-type control and showed good mating partner discrimination, suggesting that the MAP kinase cascade is not essential for chemotropism. In contrast, cells mutant for the receptor (ste2) or the β or γ subunit (ste4 and stel8) of the G protein were extremely defective in both diploid and prezygote formation and discriminated poorly between signaling and nonsignaling mating partners, implying that these components are important for chemotropism.</jats:p

Principles for the Buffering of Genetic Variation

Most genetic research has used inbred organisms and has not explored the complexity of natural genetic variation present in outbred populations. The translation of genotype to phenotype is complicated by gene interactions observed as epistasis, canalization, robustness, or buffering. Analysis of double mutations in inbred experimental organisms suggests some principles for gene interaction that may apply to natural variation as well. The buffering of variation in one gene is most often due to a small number of other genes that function in the same biochemical process. However, buffering can also result from genes functioning in processes extrinsic to that of the primary gene.</jats:p

Use of cancer-specific yeast-secreted biotinylated recombinant antibodies for serum biomarker discovery-0

bound to case-pool serum. The enriched yeast-display scFv were labeled with anti-c-myc mAb and 25 μg/ml (A,B,E,F) or 100 μg/ml (C,D,G,H) of biotinylated case (A,C,E,G) or control (B,D,F,H) serum pools, before (A-D) or after depletion by magnetic sorting (E-H). Binding signals were detected as shown with the secondary antibody 488-alexa anti-mouse Ig (488 anti-mIg) and PE-labeled streptavidin (SA-PE).<p><b>Copyright information:</b></p><p>Taken from "Use of cancer-specific yeast-secreted biotinylated recombinant antibodies for serum biomarker discovery"</p><p>http://www.translational-medicine.com/content/6/1/41</p><p>Journal of Translational Medicine 2008;6():41-41.</p><p>Published online 24 Jul 2008</p><p>PMCID:PMC2503970.</p><p></p