scholarly journals Crossing Over Is Rarely Associated With Mitotic Intragenic Recombination in Schizosaccharomyces pombe

Genetics ◽  
2001 ◽  
Vol 157 (1) ◽  
pp. 63-77 ◽  
Author(s):  
Jeffrey B Virgin ◽  
Jeffrey P Bailey ◽  
Farnaz Hasteh ◽  
James Neville ◽  
Amy Cole ◽  
...  
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Chromosomal Rearrangements ◽  
Mitotic Recombination ◽  
Intragenic Recombination ◽  
Crossing Over ◽  
Recombination Rates ◽  
Alternative Pathways ◽  
Ectopic Recombination ◽  
Specific Factors ◽  
Differential Control

Abstract Chromosomal rearrangements can result from crossing over during ectopic homologous recombination between dispersed repetitive DNA. We have previously shown that meiotic ectopic recombination between artificially dispersed ade6 heteroalleles in the fission yeast Schizosaccharomyces pombe frequently results in chromosomal rearrangements. The same recombination substrates have been studied in mitotic recombination. Ectopic recombination rates in haploids were ∼1-4 × 10-6 recombinants per cell generation, similar to allelic recombination rates in diploids. In contrast, ectopic recombination rates in heterozygous diploids were 2.5-70 times lower than allelic recombination or ectopic recombination in haploids. These results suggest that diploid-specific factors inhibit ectopic recombination. Very few crossovers occurred in ade6 mitotic recombination, either allelic or ectopic. Allelic intragenic recombination was associated with 2% crossing over, and ectopic recombination between multiple different pairing partners showed 1-7% crossing over. These results contrast sharply with the 35-65% crossovers associated with meiotic ade6 recombination and suggest either differential control of resolution of recombination intermediates or alternative pathways of recombination in mitosis and meiosis.

scholarly journals The M26 Hotspot of Schizosaccharomyces pombe Stimulates Meiotic Ectopic Recombination and Chromosomal Rearrangements

Genetics ◽  
1998 ◽  
Vol 149 (3) ◽  
pp. 1191-1204 ◽  
Author(s):  
Jeffrey B Virgin ◽  
Jeffrey P Bailey
Keyword(s):  
Homologous Recombination ◽  
Schizosaccharomyces Pombe ◽  
Dna Sequences ◽  
Chromosomal Rearrangements ◽  
Low Frequency ◽  
Repeated Sequences ◽  
Crossing Over ◽  
Ectopic Recombination ◽  
Recombination Hotspots ◽  
Integration Sites

Abstract Homologous recombination is increased during meiosis between DNA sequences at the same chromosomal position (allelic recombination) and at different chromosomal positions (ectopic recombination). Recombination hotspots are important elements in controlling meiotic allelic recombination. We have used artificially dispersed copies of the ade6 gene in Schizosaccharomyces pombe to study hotspot activity in meiotic ectopic recombination. Ectopic recombination was reduced 10–1000-fold relative to allelic recombination, and was similar to the low frequency of ectopic recombination between naturally repeated sequences in S. pombe. The M26 hotspot was active in ectopic recombination in some, but not all, integration sites, with the same pattern of activity and inactivity in ectopic and allelic recombination. Crossing over in ectopic recombination, resulting in chromosomal rearrangements, was associated with 35–60% of recombination events and was stimulated 12-fold by M26. These results suggest overlap in the mechanisms of ectopic and allelic recombination and indicate that hotspots can stimulate chromosomal rearrangements.

scholarly journals Isolation and characterization of Schizosaccharomyces pombe mutants affected in mitotic recombination.

Genetics ◽  
1991 ◽  
Vol 128 (3) ◽  
pp. 495-504
Author(s):  
A Gysler-Junker ◽  
Z Bodi ◽  
J Kohli
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Mitotic Recombination ◽  
Selective Medium ◽  
Intragenic Recombination ◽  
Crossing Over ◽  
Wild Type ◽  
Isolation And Characterization ◽  
Mitotic Gene Conversion ◽  
Type Frequency

Abstract A haploid Schizosaccharomyces pombe strain carrying a heteroallelic duplication of the ade6 gene was used to isolate mitotic recombination-deficient mutants. Recombination between the different copies of the ade6 gene can lead to Ade+ segregants. These are observed as growing papillae when colonies of a suitable size are replicated onto selective medium. We isolated mutants which show an altered papillation phenotype. With two exceptions, they exhibit a decrease in the frequency of mitotic recombination between the heteroalleles of the duplication. The two other mutants display a hyper-recombination phenotype. The 12 mutations were allocated to at least nine distinct loci by recombination tests. Of the eight rec mutants analyzed further, six were also affected in mitotic intergenic recombination in the intervals cen2-mat or cen3-arg 1. No effect on mitotic intragenic recombination was observed. These data suggest that mitotic gene conversion and crossing over can be separated mutationally. Meiotic recombination occurs at the wild-type frequency in all mutants investigated.

scholarly journals The Ade6-M26 Mutation of Schizosaccharomyces Pombe Increases the Frequency of Crossing over.

Genetics ◽  
1988 ◽  
Vol 119 (3) ◽  
pp. 507-515
Author(s):  
P Schuchert ◽  
J Kohli
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Marker Gene ◽  
Crossing Over ◽  
Crossover Frequency ◽  
Tetrad Analysis ◽  
Ectopic Recombination ◽  
Homologous Sequences ◽  
New Information ◽  
Conversion Frequency

Abstract The ade6-M26 mutation of Schizosaccharomyces pombe increases conversion frequency in comparison with the nearby mutation ade6-M375. In order to investigate the effect of ade6-M26 on crossover frequency, heteroallelic ade6 duplications were constructed by integration of plasmids carrying the marker gene ura4. One ade6 gene carries either of the mutations M26 or M375 while the other ade6 copy carries the L469 mutation in both duplications. The duplication with ade6-M26 yields Ade(+) recombinants at significantly higher frequencies in meiosis, but not in mitosis. Tetrad analysis and physical characterization of spore clones from recombination tetrads demonstrate that conversions, unequal crossovers and intrachromatid exchanges occur at higher frequencies but with unaltered proportions among them. The conversion events show a pronounced bias when M26 is involved: they take place preferentially at the M26 allele. Thus the ade6-M26 mutation not only enhances conversion frequency as demonstrated before, but also crossover frequency. It displays the properties expected for a preferred site of initiation of general meiotic recombination. The duplications also yielded new information on ectopic recombination in S. pombe: ectopic crossovers occur in the duplications at much higher frequency than among naturally dispersed homologous sequences.

scholarly journals Position effects in ectopic and allelic mitotic recombination in Saccharomyces cerevisiae.

Genetics ◽  
1989 ◽  
Vol 123 (2) ◽  
pp. 261-268 ◽  
Author(s):  
M Lichten ◽  
J E Haber
Keyword(s):  
Meiotic Recombination ◽  
Chromosomal Location ◽  
Mitotic Recombination ◽  
Yeast Genome ◽  
Intragenic Recombination ◽  
Position Effects ◽  
Ectopic Recombination ◽  
Leu2 Gene ◽  
Genomic Location ◽  
Strong Position

Abstract We have examined the role that genomic location plays in mitotic intragenic recombination. Mutant alleles of the LEU2 gene were inserted at five locations in the yeast genome. Diploid and haploid strains containing various combinations of these inserts were used to examine both allelic recombination (between sequences at the same position on parental homologs) and ectopic recombination (between sequences at nonallelic locations). Chromosomal location had little effect on mitotic allelic recombination. The rate of recombination to LEU2 at five different loci varied less than threefold. This finding contrasts with previous observations of strong position effects in meiosis; frequencies of meiotic recombination at the same five loci differ by about a factor of forty. Mitotic recombination between dispersed copies of leu2 displayed strong position effects. Copies of leu2 located approximately 20 kb apart on the same chromosome recombined at rates 6-13-fold higher than those observed for allelic copies of leu2. leu2 sequences located on nonhomologous chromosomes or at distant loci on the same chromosome recombined at rates similar to those observed for allelic copies. We suggest that, during mitosis, parental homologs interact with each other no more frequently than do nonhomologous chromosomes.

scholarly journals Effects of mutagen-sensitive mus mutations on spontaneous mitotic recombination in Aspergillus.

Genetics ◽  
1992 ◽  
Vol 130 (4) ◽  
pp. 717-728
Author(s):  
P Zhao ◽  
E Kafer
Keyword(s):  
Mitotic Recombination ◽  
Dna Lesions ◽  
Intragenic Recombination ◽  
Chromosome Loss ◽  
Crossing Over ◽  
Induced Mutants ◽  
Radiation Induced ◽  
Mitotic Gene Conversion ◽  
Single Allele ◽  
Repair Genes

Abstract Methyl methane-sulfonate (MMS)-sensitive, radiation-induced mutants of Aspergillus were shown to define nine new DNA repair genes, musK to musS. To test mus mutations for effects on mitotic recombination, intergenic crossing over was assayed between color markers and their centromeres, and intragenic recombination between two distinguishable adE alleles. Of eight mutants analyzed, four showed significant deviations from mus+ controls in both tests. Two mutations, musK and musL, reduced recombination, while musN and musQ caused increases. In contrast, musO diploids produced significantly higher levels only for intragenic recombination. Effects were relatively small, but averages between hypo- and hyperrec mus differed 15-20-fold. In musL diploids, most of the rare color segregants resulted from mitotic malsegregation rather than intergenic crossing over. This indicates that the musL gene product is required for recombination and that DNA lesions lead to chromosome loss when it is deficient. In addition, analysis of the genotypes of intragenic (ad+) recombinants showed that the musL mutation specifically reduced single allele conversion but increased complex conversion types (especially recombinants homozygous for ad+). Similar analysis revealed differences between the effects of two hyperrec mutations; musN apparently caused high levels solely of mitotic crossing over, while musQ increased various conversion types but not reciprocal crossovers. These results suggest that mitotic gene conversion and crossing over, while generally associated, are affected differentially in some of the mus strains of Aspergillus nidulans.

scholarly journals Active and inactive transplacement of the M26 recombination hotspot in Schizosaccharomyces pombe.

Genetics ◽  
1995 ◽  
Vol 141 (1) ◽  
pp. 33-48
Author(s):  
J B Virgin ◽  
J Metzger ◽  
G R Smith
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Meiotic Recombination ◽  
Plasmid Dna ◽  
Context Effect ◽  
Intragenic Recombination ◽  
Multicopy Plasmid ◽  
Chromosomal Locus ◽  
Sequence Element ◽  
Recombination Hotspot ◽  
Recombination Hotspots

Abstract The ade6-M26 mutation of the fission yeast Schizosaccharomyces pombe creates a meiotic recombination hotspot that elevates ade6 intragenic recombination approximately 10-15-fold. A heptanucleotide sequence including the M26 point mutation is required but not sufficient for hotspot activity. We studied the effects of plasmid and chromosomal context on M26 hotspot activity. The M26 hotspot was inactive on a multicopy plasmid containing M26 embedded within 3.0 or 5.9 kb of ade6 DNA. Random S. pombe genomic fragments totaling approximately 7 Mb did not activate the M26 hotspot on a plasmid. M26 hotspot activity was maintained when 3.0-, 4.4-, and 5.9-kb ade6-M26 DNA fragments, with various amounts of non-S. pombe plasmid DNA, were integrated at the ura4 chromosomal locus, but only in certain configurations relative to the ura4 gene and the cointegrated plasmid DNA. Several integrations created new M26-independent recombination hotspots. In all cases the non-ade6 DNA was located > 1 kb from the M26 site, and in some cases > 2 kb. Because the chromosomal context effect was transmitted over large distances, and did not appear to be mediated by a single discrete DNA sequence element, we infer that the local chromatin structure has a pronounced effect on M26 hotspot activity.

scholarly journals A 160-bp Palindrome Is a Rad50·Rad32-Dependent Mitotic Recombination Hotspot inSchizosaccharomyces pombe

Genetics ◽  
2002 ◽  
Vol 161 (1) ◽  
pp. 461-468 ◽  
Author(s):  
Joseph A Farah ◽  
Edgar Hartsuiker ◽  
Ken-ichi Mizuno ◽  
Kunihiro Ohta ◽  
Gerald R Smith
Keyword(s):  
Secondary Structure ◽  
Schizosaccharomyces Pombe ◽  
Inverted Repeat ◽  
Mitotic Recombination ◽  
Genome Integrity ◽  
Recombination Hotspot ◽  
Nuclease Domain ◽  
Palindromic Sequences

AbstractPalindromic sequences can form hairpin and cruciform structures that pose a threat to genome integrity. We found that a 160-bp palindrome (an inverted repeat of 80 bp) conferred a mitotic recombination hotspot relative to a control nonpalindromic sequence when inserted into the ade6 gene of Schizosaccharomyces pombe. The hotspot activity of the palindrome, but not the basal level of recombination, was abolished by a rad50 deletion, by a rad50S “separation of function” mutation, or by a rad32-D25A mutation in the nuclease domain of the Rad32 protein, an Mre11 homolog. We propose that upon extrusion of the palindrome the Rad50·Rad32 nuclease complex recognizes and cleaves the secondary structure thus formed and generates a recombinogenic break in the DNA.

scholarly journals INDUCTION OF MITOTIC CROSSING OVER IN SACCHAROMYCES CEREVISIAE BY BREAKDOWN PRODUCTS OF DIMETHYLNITROSAMINE, DIETHYLNITROSAMINE, 1-NAPHTHYLAMINE AND 2-NAPHTHYLAMINE FORMED BY AN IN VITRO HYDROXYLATION SYSTEM

Genetics ◽  
1973 ◽  
Vol 74 (3) ◽  
pp. 433-442
Author(s):  
V W Mayer
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mitotic Recombination ◽  
Crossing Over ◽  
Genetic Damage ◽  
Nitroso Group ◽  
Damage Potential ◽  
Test Conditions

ABSTRACT Dimethylnitrosamine and diethylnitrosamine, two potent carcinogens, are nonmutagenic when tested directly in microorganisms. Likewise 1-naphthylamine and 2-naphthylamine are also nonmutagenic but the N-hydroxy derivatives are mutagenic in microorganisms. Apparently these compounds require metabolism to breakdown products which are then the proximately active agents, and microorganisms lack the enzymes necessary to effect this conversion. These compounds are mutagenic in Saccharomyces after conversion to breakdown products in an in vitro hydroxylation medium. The induction of mitotic crossing over in Saccharomyces cerevisiae by breakdown products of dimethylnitrosamine, diethylnitrosamine, 1-naphthylamine and 2-naphthylamine formed in the Udenfriend hydroxylation medium is reported in this communication. Mitotic crossing over was detected as red sectored colonies resulting from induced homozygosity of the ade2 marker. Dimethylamine and diethylamine, which lack the nitroso group of the nitrosamines, did not induce mitotic crossing over under any of the test conditions. To further confirm that the induced sectored colonies were the result of mitotic crossing over they were tested for the presence of reciprocal products. The expected reciprocal products were found in over 67% of the isolates tested. The significance and practicality of using mitotic recombination as an indicator of genetic damage potential of chemicals is discussed.

scholarly journals Possible role of natural selection in the formation of tandem-repetitive noncoding DNA.

Genetics ◽  
1994 ◽  
Vol 136 (1) ◽  
pp. 333-341
Author(s):  
W Stephan ◽  
S Cho
Keyword(s):  
Natural Selection ◽  
Satellite Dna ◽  
Repeat Length ◽  
Crossing Over ◽  
Recombination Rates ◽  
Noncoding Dna ◽  
Satellite Dnas ◽  
Unequal Crossing Over ◽  
Wide Range ◽  
Long Range Ordering

Abstract A simulation model of sequence-dependent amplification, unequal crossing over and mutation is analyzed. This model predicts the spontaneous formation of tandem-repetitive patterns of noncoding DNA from arbitrary sequences for a wide range of parameter values. Natural selection is found to play an essential role in this self-organizing process. Natural selection which is modeled as a mechanism for controlling the length of a nucleotide string but not the sequence itself favors the formation of tandem-repetitive structures. Two measures of sequence heterogeneity, inter-repeat variability and repeat length, are analyzed in detail. For fixed mutation rate, both inter-repeat variability and repeat length are found to increase with decreasing rates of (unequal) crossing over. The results are compared with data on micro-, mini- and satellite DNAs. The properties of minisatellites and satellite DNAs resemble the simulated structures very closely. This suggests that unequal crossing over is a dominant long-range ordering force which keeps these arrays homogeneous even in regions of very low recombination rates, such as at satellite DNA loci. Our analysis also indicates that in regions of low rates of (unequal) crossing over, inter-repeat variability is maintained at a low level at the expense of much larger repeat units (multimeric repeats), which are characteristic of satellite DNA. In contrast, the microsatellite data do not fit the proposed model well, suggesting that unequal crossing over does not act on these very short tandem arrays.

scholarly journals Genetic and physical analysis of the M26 recombination hotspot of Schizosaccharomyces pombe.

Genetics ◽  
1988 ◽  
Vol 119 (3) ◽  
pp. 491-497
Author(s):  
A S Ponticelli ◽  
E P Sena ◽  
G R Smith
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Meiotic Recombination ◽  
Base Pair ◽  
Initiation Site ◽  
Mitotic Recombination ◽  
Physical Analysis ◽  
Nucleotide Change ◽  
Recombination Hotspot ◽  
Base Pair Mismatch

Abstract The ade6-M26 mutation of Schizosaccharomyces pombe has previously been reported to stimulate ade6 intragenic meiotic recombination. We report here that the ade6-M26 mutation is a single G----T nucleotide change, that M26 stimulated recombination within ade6 but not at other distinct loci, and that M26 stimulated meiotic but not mitotic recombination. In addition, M26 stimulated recombination within ade6 when M26 is homozygous; this result demonstrates that a base-pair mismatch at the M26 site was not required for the stimulation. These results are consistent with the ade6-M26 mutation creating a meiotic recombination initiation site.

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