Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Saccharomyces cerevisiae has been used widely both as a model system for unraveling the biochemical, genetic, and molecular details of gene expression and the secretion process, and as a host for the production of heterologous proteins of biotechnological interest. The potential of starch as a renewable biological resource has stimulated research into amylolytic enzymes and the broadening of the substrate range of S. cerevisiae. The enzymatic hydrolysis of starch, consisting of linear (amylose) and branched glucose polymers (amylopectin), is catalyzed by alpha- and beta-amylases, glucoamylases, and debranching enzymes, e.g., pullulanases. Starch utilization in the yeast S. cerevisiae var. diastaticus depends on the expression of the three unlinked genes, STA1 (chr. IV), STA2 (chr. II), and STA3 (chr. XIV), each encoding one of the extracellular glycosylated glucoamylases isozymes GAI, GAII, or GAIII, respectively. The restriction endonuclease maps of STA1, STA2, and STA3 are identical. These genes are absent in S. cerevisiae, but a related gene, SGA1, encoding an intracellular, sporulation-specific glucoamylase (SGA), is present. SGA1 is homologous to the middle and 3' regions of the STA genes, but lacks a 5' sequence that encodes the domain for secretion of the extracellular glucoamylases. The STA genes are positively regulated by the presence of three GAM genes. In addition to positive regulation, the STA genes are regulated negatively at three levels. Whereas strains of S. diastaticus are capable of expressing the STA genes, most strains of S. cerevisiae contain STA10, whose presence represses the expression of the STA genes in an undefined manner. The STA genes are also repressed in diploid cells, presumably by the MATa/MAT alpha-encoded repressor. STA gene expression is reduced in liquid synthetic media, it is carbon catabolite repressed by glucose, and is inhibited in petite mutants.
...
PMID:The glucoamylase multigene family in Saccharomyces cerevisiae var. diastaticus: an overview. 187 99

We have identified two novel intermediates of homothallic switching of the yeast mating type gene, from MATa to MAT alpha. Following HO endonuclease cleavage, 5' to 3' exonucleolytic digestion is observed distal to the HO cut, creating a 3'-ended single-stranded tail. This recision is more extensive in a rad52 strain unable to switch. Surprisingly, the proximal side of the HO cut is protected from degradation; this stabilization depends on the presence of the silent copy donor sequences. A second intermediate was identified by a quantitative application of the polymerase chain reaction (PCR). The Y alpha-MAT distal covalent fragment of the switched product appears 30 min prior to the appearance of the MAT proximal Y alpha junction. No covalent joining of MAT distal to HML distal sequences is detected. We suggested that the MAT DNA distal to the HO cut invades the intact donor and is extended by DNA synthesis. This step is prevented in a rad52 strain. These intermediates are consistent with a model for MAT switching in which only the distal side of the HO cut is initially active in strand invasion and transfer of information from the donor.
...
PMID:Intermediates of recombination during mating type switching in Saccharomyces cerevisiae. 217 24

The kinetics of mating type switching in Saccharomyces cerevisiae can be followed at the DNA level by using a galactose-inducible HO (GAL-HO) gene to initiate the event in synchronously growing cells. From the time that HO endonuclease cleaves MAT a until the detection of MAT alpha DNA took 60 min. When unbudded G1-phase cells were induced, switched to the opposite mating type in "pairs." In the presence of the DNA synthesis inhibitor hydroxyurea, HO-induced cleavage occurred but cells failed to complete switching. In these blocked cells, the HO-cut ends of MATa remained stable for at least 3 h. Upon removal of hydroxyurea, the cells completed the switch in approximately 1 h. The same kinetics of MAT switching were also seen in asynchronous cultures and when synchronously growing cells were induced at different times of the cell cycle. Thus, the only restriction that confined normal homothallic switching to the G1 phase of the cell cycle was the expression of HO endonuclease. Further evidence that galactose-induced cells can switch in the G2 phase of the cell cycle was the observation that these cells did not always switch in pairs. This suggests that two chromatids, both cleaved with HO endonuclease, can interact independently with the donors HML alpha and HMRa.
...
PMID:Physical monitoring of mating type switching in Saccharomyces cerevisiae. 284 79

HO nuclease is a site-specific double-strand endonuclease present in haploid Saccharomyces cerevisiae undergoing mating type interconversion. HO nuclease initiates mating type interconversion by making a double-strand break within the MAT locus. To define the recognition site for the enzyme in vitro, we have constructed a number of point mutations and deletions within or adjacent to the HO recognition site. Digestion of these substrates with HO in vitro reveals that the minimal recognition site is 18 base pairs long, although several shorter substrates and substrates containing point mutations are cleaved at low levels in vitro. A 24-base-pair HO recognition site stimulates homologous recombination when present in a region unrelated to MAT. Recombinants arise from both gene conversion and crossover events. The identification of the HO recognition site provides a way of introducing a defined initiation site for recombination.
...
PMID:A 24-base-pair DNA sequence from the MAT locus stimulates intergenic recombination in yeast. 302 May 59

We investigated the effects of double-strand breaks on meiotic recombination in yeast. A double-strand break was introduced at the MATa locus by sporulation of a MAT alpha inc/MATa diploid under inducing conditions for the HO-encoded endonuclease; 14% of the resulting tetrads had undergone 4 alpha:0a conversion. Conversion at MAT was associated with co-conversion of a closely linked marker and an increased recombination frequency for flanking markers. We also studied the sporulation products of a diploid heterozygous at the HIS4 locus for an insertion of a 100 bp fragment of MATa containing the HO endonuclease cut site. Under inducing conditions, a significant number of tetrads were formed that had undergone gene conversions in favor of the HIS4+ allele. Although double-strand breaks can initiate meiotic recombination in yeast, the data suggest that they do not normally do so.
...
PMID:Double-strand breaks can initiate meiotic recombination in S. cerevisiae. 352 43

Homothallic switching of the mating type genes of Saccharomyces cerevisiae occurs by a gene conversion event, replacing sequences at the expressed MAT locus with a DNA segment copied from one of two unexpressed loci, HML or HMR. The transposed Ya or Y alpha sequences are flanked by homologous regions that are believed to be essential for switching. We examined the transposition of a mating type gene (hmr alpha 1-delta 6) which contains a 150-base-pair deletion spanning the site where the HO endonuclease generates a double-stranded break in MAT that initiates the gene conversion event. Despite the fact that the ends of the cut MAT region no longer share homology with the donor hmr alpha 1-delta 6, switching of MATa or MAT alpha to mat alpha 1-delta 6 was efficient. However, there was a marked increase in the number of aberrant events, especially the formation of haploid-inviable fusions between MAT and the hmr alpha 1-delta 6 donor locus.
...
PMID:Homothallic switching of Saccharomyces cerevisiae mating type genes by using a donor containing a large internal deletion. 391 86

Cell type in Saccharomyces yeasts is regulated by two transposable blocks of DNA, the a and alpha cassettes. There are three loci where either cassette can exist. At the HML and HMR loci the cassettes are not expressed. The cassette at the MAT locus is expressed and controls the cell type. Changes of cell type involve transposition-substitution of cassettes from HML or HMR into MAT. We recently reported the molecular cloning of the alpha cassette at the HML locus, HML alpha, and showed that it contained sequences homologous to HMR and MAT. Using HML alpha as a hybridization probe, we have isolated HMLa, HMR alpha, HMRa, MAT alpha, and MATa. Heteroduplex analysis and restriction endonuclease mapping studies indicate that the a and alpha cassettes differ by a substitution corresponding to about 750 base pairs in alpha and about 600 base pairs in a. The HML, HMR, and MAT loci have regions of homology flanking the position of the a versus alpha substitution. We have used specific chromosome rearrangements fusing MAT and HML and MAT with HMR to orient the cloned sequences on the genetic map and have found that all three genes have the same left-to-right polarity on the chromosome.
...
PMID:Structure and organization of transposable mating type cassettes in Saccharomyces yeasts. 624 70

In the yeast Saccharomyces cerevisiae there are two mating types, a and alpha, which may mate to produce an a/alpha diploid. Mating type is determined by the allele (MATa or MAT alpha) occupying the MAT locus. In a diploid, expression of the MATa1 and MAT alpha 2 genes determines the a/alpha state by regulating the expression of unlinked genes. Previous S1 endonuclease mapping implied that the MATa1 transcript is not processed. We have performed further S1 mapping of this transcript, demonstrating that the MATa1 gene contains two introns, unlike any other characterized nuclear gene in yeast. Both introns contain 5' splice sites and 5'- TACTAACA -3' consensus sequences at the positions predicted by the S1 mapping data. In the splicing-defective rna2 mutant, the mature message disappears rapidly and the precursor RNA accumulates. The RNA processing removes the UGA stop codon which was previously believed to be read-through.
...
PMID:The yeast MATa1 gene contains two introns. 632 35

HO endonuclease-induced double-strand breaks (DSBs) in the yeast Saccharomyces cerevisiae can be repaired by the process of gap repair or, alternatively, by single-strand annealing if the site of the break is flanked by directly repeated homologous sequences. We have shown previously (J. Fishman-Lobell and J. E. Haber, Science 258:480-484, 1992) that during the repair of an HO-induced DSB, the excision repair gene RAD1 is needed to remove regions of nonhomology from the DSB ends. In this report, we present evidence that among nine genes involved in nucleotide excision repair, only RAD1 and RAD10 are required for removal of nonhomologous sequences from the DSB ends. rad1 delta and rad10 delta mutants displayed a 20-fold reduction in the ability to execute both gap repair and single-strand annealing pathways of HO-induced recombination. Mutations in RAD2, RAD3, and RAD14 reduced HO-induced recombination by about twofold. We also show that RAD7 and RAD16, which are required to remove UV photodamage from the silent HML, locus, are not required for MAT switching with HML or HMR as a donor. Our results provide a molecular basis for understanding the role of yeast nucleotide excision repair gene and their human homologs in DSB-induced recombination and repair.
...
PMID:RAD1 and RAD10, but not other excision repair genes, are required for double-strand break-induced recombination in Saccharomyces cerevisiae. 789 18

In haploid rad52 Saccharomyces cerevisiae strains unable to undergo homologous recombination, a chromosomal double-strand break (DSB) can be repaired by imprecise rejoining of the broken chromosome ends. We have used two different strategies to generate broken chromosomes: (i) a site-specific DSB generated at the MAT locus by HO endonuclease cutting or (ii) a random DSB generated by mechanical rupture during mitotic segregation of a conditionally dicentric chromosome. Broken chromosomes were repaired by deletions that were highly variable in size, all of which removed more sequences than was required either to prevent subsequent HO cleavage or to eliminate a functional centromere, respectively. The junction of the deletions frequently occurred where complementary strands from the flanking DNA could anneal to form 1 to 5 bp, although 12% (4 of 34) of the events appear to have occurred by blunt-end ligation. These types of deletions are very similar to the junctions observed in the repair of DSBs by mammalian cells (D. B. Roth and J. H. Wilson, Mol. Cell. Biol. 6:4295-4304, 1986). When a high level of HO endonuclease, expressed in all phases of the cell cycle, was used to create DSBs, we also recovered a large class of very small (2- or 3-bp) insertions in the HO cleavage site. These insertions appear to represent still another mechanism of DSB repair, apparently by annealing and filling in the overhanging 3' ends of the cleavage site. These types of events have also been well documented for vertebrate cells.
...
PMID:Two different types of double-strand breaks in Saccharomyces cerevisiae are repaired by similar RAD52-independent, nonhomologous recombination events. 828 8


1 2 3 4 5 Next >>

---