scholarly journals FREQUENCY AND DIRECTIONALITY OF GENE CONVERSION EVENTS INVOLVING THE CYC7-H3 MUTATION IN SACCHAROMYCES CEREVISIAE

Genetics ◽  
1986 ◽  
Vol 114 (2) ◽  
pp. 347-361
Author(s):  
Patricia J Pukkila ◽  
Michael D Stephens ◽  
David M Binninger ◽  
Beverly Errede
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Gene Conversion ◽  
High Frequency ◽  
Yeast Genome ◽  
Junction Region ◽  
Sequence Comparisons ◽  
Site Specific ◽  
Site Specific Recombination ◽  
Conversion Frequency ◽  
Aberrant Segregation

ABSTRACT The CYC7-H3 mutation is a 5-kb deletion that causes overproduction of iso-2 cytochrome c. Unlike most mutations in yeast, the CYC7-H3 mutation is preferentially lost when it is involved in a gene conversion event. We have shown that cloned copies of CYC7-H3 DNA that are inserted into the yeast genome are associated with a high frequency of recombination and aberrant segregation events. Since parity in conversion frequency was observed when the extensive insertion/deletion heterozygosity at this locus was eliminated, we conclude that the CYC7-H3 sequences are inherently capable of acting as donors or recipients in gene conversion events, although they are unlikely to act as donors when they are located opposite a large heterology. DNA sequence comparisons revealed similarities between the CYC7-H3 junction region and the 2-µm circle DNA region that is involved in site-specific recombination.

scholarly journals GENE CONVERSION AND INTRAGENIC RECOMBINATION AT AT THE SUP6 LOCUS AND THE SURROUNDING REGION IN SACCHAROMYCES CEREVISIAE

Genetics ◽  
1976 ◽  
Vol 84 (4) ◽  
pp. 697-721
Author(s):  
Laura Dicaprio ◽  
P J Hastings
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Gene Conversion ◽  
High Frequency ◽  
High Conversion ◽  
Intragenic Recombination ◽  
Maximum Frequency ◽  
Haploid Strain ◽  
Meiotic Gene ◽  
Conversion Frequency

ABSTRACT Spontaneous secondary mutations of the ochre suppressor SUP6 were selected in a haploid strain of Saccharomyces cerevisiae. Unselected tetrads were dissected from crosses heterozygous for one of three alleles of SUP6 and for three other loci in this region which span a length of 14 map units (his2, cdc14 and met10). The study showed that all of these markers were characterized by high frequency of meiotic gene conversion and long conversion lengths which frequently extended into adjacent marked loci. Despite the high conversion frequency of SUP6, recombination between alleles of this locus reached a maximum frequency of only 2 × 10-3 prototrophs/spore. Although the allelic recombination frequencies were not distance dependent and consequently could not be used to order the alleles, the inequality between the two recombinant outside marker combinations among selected intragenic recombinants produced an internally consistent map of the suppressor locus. Recombination at SUP6 (whether detected as conversion in tetrads or the production of recombinants among random spores) was accompanied by significantly less than 50% outside marker recombination.

scholarly journals Punctuated Aneuploidization of the Budding Yeast Genome

Genetics ◽  
2020 ◽  
Vol 216 (1) ◽  
pp. 43-50 ◽  
Author(s):  
Lydia R. Heasley ◽  
Ruth A. Watson ◽  
Juan Lucas Argueso
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Tumor Cells ◽  
Genomic Instability ◽  
High Frequency ◽  
Budding Yeast ◽  
Cell Types ◽  
Eukaryotic Cell ◽  
Yeast Genome ◽  
Single Chromosome ◽  
Brewing Yeasts

Remarkably complex patterns of aneuploidy have been observed in the genomes of many eukaryotic cell types, ranging from brewing yeasts to tumor cells. Such aberrant karyotypes are generally thought to take shape progressively over many generations, but evidence also suggests that genomes may undergo faster modes of evolution. Here, we used diploid Saccharomyces cerevisiae cells to investigate the dynamics with which aneuploidies arise. We found that cells selected for the loss of a single chromosome often acquired additional unselected aneuploidies concomitantly. The degrees to which these genomes were altered fell along a spectrum, ranging from simple events affecting just a single chromosome, to systemic events involving many. The striking complexity of karyotypes arising from systemic events, combined with the high frequency at which we detected them, demonstrates that cells can rapidly achieve highly altered genomic configurations during temporally restricted episodes of genomic instability.

scholarly journals Deletions extending from a single Ty1 element in Saccharomyces cerevisiae.

1985 ◽  
Vol 5 (12) ◽  
pp. 3451-3457 ◽  
Author(s):  
K M Downs ◽  
G Brennan ◽  
S W Liebman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cytochrome C ◽  
Reciprocal Translocation ◽  
Restriction Site ◽  
Chromosomal Rearrangements ◽  
Yeast Cells ◽  
Site Specific ◽  
Site Specific Recombination ◽  
The Third ◽  
Deletion Junction

Chromosomal rearrangements associated with one Ty1 element in the iso-1-cytochrome c (CYC1) region of Saccharomyces cerevisiae yeast cells were examined. Most of the rearrangements were deletions of the three linked genes, CYC1, OSM1, and RAD7, and resulted from recombination involving the single Ty1 element and a solo delta in the same orientation. These deletions differed by the number of Ty1 elements (zero, one, or two) remaining after deletion and by restriction site heterogeneities associated with these elements. A single Ty1 element remained at the deletion junction point much more frequently than no Ty1. Apparently the Ty1-associated delta element nearer to the solo delta was involved more often in recombination than the more distal Ty1-associated delta element. The restriction site data implicate gene conversion and suggest that site-specific recombination within the deltas, if occurring, is not the only mechanism of delta-delta recombination. Three other rearrangements bore deletions which began at the end of the Ty1 element and extended into regions not bearing Ty1 or delta sequences. Two of these deletions eliminated 7 kilobases of DNA, although they differed by an associated reciprocal translocation. The third involved a deletion of 14.7 kilobases of DNA associated with an overlapping inversion.

scholarly journals Xer1-Mediated Site-Specific DNA Inversions and Excisions in Mycoplasma agalactiae

2010 ◽  
Vol 192 (17) ◽  
pp. 4462-4473 ◽  
Author(s):  
Stefan Czurda ◽  
Wolfgang Jechlinger ◽  
Renate Rosengarten ◽  
Rohini Chopra-Dewasthaly
Keyword(s):  
High Frequency ◽  
Phase Variation ◽  
Etiologic Agent ◽  
Reporter System ◽  
Recognition Sequence ◽  
Site Specific ◽  
Phase Switching ◽  
Site Specific Recombination ◽  
Mycoplasma Agalactiae ◽  
Variable Surface

ABSTRACT Surface antigen variation in Mycoplasma agalactiae, the etiologic agent of contagious agalactia in sheep and goats, is governed by site-specific recombination within the vpma multigene locus encoding the Vpma family of variable surface lipoproteins. This high-frequency Vpma phase switching was previously shown to be mediated by a Xer1 recombinase encoded adjacent to the vpma locus. In this study, it was demonstrated in Escherichia coli that the Xer1 recombinase is responsible for catalyzing vpma gene inversions between recombination sites (RS) located in the 5′-untranslated region (UTR) in all six vpma genes, causing cleavage and strand exchange within a 21-bp conserved region that serves as a recognition sequence. It was further shown that the outcome of the site-specific recombination event depends on the orientation of the two vpma RS, as direct or inverted repeats. While recombination between inverted vpma RS led to inversions, recombination between direct repeat vpma RS led to excisions. Using a newly developed excision assay based on the lacZ reporter system, we were able to successfully demonstrate under native conditions that such Xer1-mediated excisions can indeed also occur in the M. agalactiae type strain PG2, whereas they were not observed in the control xer1-disrupted VpmaY phase-locked mutant (PLMY), which lacks Xer1 recombinase. Unless there are specific regulatory mechanisms preventing such excisions, this might be the cost that the pathogen has to render at the population level for maintaining this high-frequency phase variation machinery.

scholarly journals Rearrangements occurring adjacent to a single Ty1 yeast retrotransposon in the presence and absence of full-length Ty1 transcription.

Genetics ◽  
1992 ◽  
Vol 131 (4) ◽  
pp. 833-850
Author(s):  
P R Sutton ◽  
S W Liebman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Homologous Recombination ◽  
Transposable Element ◽  
Gene Conversion ◽  
Genetic Background ◽  
Repetitive Sequences ◽  
Full Length ◽  
Yeast Genome ◽  
Yeast Saccharomyces Cerevisiae ◽  
Ty1 Retrotransposon

Abstract The structures of two unusual deletions from the yeast Saccharomyces cerevisiae are described. These deletions extend from a single Ty1 retrotransposon to an endpoint near a repetitive tRNA(Gly) gene. The deletions suggest that unique sequences flanked by two nonidentical repetitive sequences, or bordered on only one side by a transposable element, have the potential to be mobilized in the yeast genome. Models for the formation of these two unusual deletions were tested by isolating and analyzing 32 additional unusual deletions of the CYC1 region that extend from a single Ty1 retrotransposon. Unlike the most common class of deletions recovered in this region, these deletions are not attributable solely to homologous recombination among repetitive Ty1 or delta elements. They arose by two distinct mechanisms. In an SPT8 genetic background, most unusual deletions arose by transposition of a Ty1 element to a position adjacent to a tRNA(Gly) gene followed by Ty1-Ty1 recombination. In an spt8 strain, where full-length Ty1 transcription and, therefore, transposition are reduced, most deletions were due to gene conversion of a 7-kb chromosomal interval flanked by a Ty1 element and a tRNA(Gly) gene.

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