Genetics of genetics in Drosophila: P elements serving the study of homologous recombination, gene conversion and targeting

Chromosoma ◽  
1995 ◽  
Vol 103 (10) ◽  
pp. 659-668 ◽  
Author(s):  
Dirk-Henner Lankenau
Keyword(s):  
Homologous Recombination ◽  
Gene Conversion ◽  
P Elements ◽  
Recombination Gene

scholarly journals The Role of Blm Helicase in Homologous Recombination, Gene Conversion Tract Length, and Recombination Between Diverged Sequences inDrosophilamelanogaster

Genetics ◽  
2017 ◽  
Vol 207 (3) ◽  
pp. 923-933 ◽  
Author(s):  
Henry A. Ertl ◽  
Daniel P. Russo ◽  
Noori Srivastava ◽  
Joseph T. Brooks ◽  
Thu N. Dao ◽  
...  
Keyword(s):  
Homologous Recombination ◽  
Gene Conversion ◽  
Tract Length ◽  
Blm Helicase ◽  
Gene Conversion Tract ◽  
Conversion Tract ◽  
Recombination Gene

scholarly journals Gene Conversion Tracts from Double-Strand Break Repair in Mammalian Cells

1998 ◽  
Vol 18 (1) ◽  
pp. 93-101 ◽  
Author(s):  
Beth Elliott ◽  
Christine Richardson ◽  
Jamie Winderbaum ◽  
Jac A. Nickoloff ◽  
Maria Jasin
Keyword(s):  
Homologous Recombination ◽  
Gene Conversion ◽  
Gene Targeting ◽  
Mammalian Cells ◽  
Embryonic Stem ◽  
Sequence Divergence ◽  
Recombinational Repair ◽  
Exogenous Dna ◽  
Extensive Degradation ◽  
Recombination Gene

ABSTRACT Mammalian cells are able to repair chromosomal double-strand breaks (DSBs) both by homologous recombination and by mechanisms that require little or no homology. Although spontaneous homologous recombination is rare, DSBs will stimulate recombination by 2 to 3 orders of magnitude when homology is provided either from exogenous DNA in gene-targeting experiments or from a repeated chromosomal sequence. Using a gene-targeting assay in mouse embryonic stem cells, we now investigate the effect of heterology on recombinational repair of DSBs. Cells were cotransfected with an endonuclease expression plasmid to induce chromosomal DSBs and with substrates containing up to 1.2% heterology from which to repair the DSBs. We find that heterology decreases the efficiency of recombinational repair, with 1.2% sequence divergence resulting in an approximately sixfold reduction in recombination. Gene conversion tract lengths were examined in 80 recombinants. Relatively short gene conversion tracts were observed, with 80% of the recombinants having tracts of 58 bp or less. These results suggest that chromosome ends in mammalian cells are generally protected from extensive degradation prior to recombination. Gene conversion tracts that were long (up to 511 bp) were continuous, i.e., they contained an uninterrupted incorporation of the silent mutations. This continuity suggests that these long tracts arose from extensive degradation of the ends or from formation of heteroduplex DNA which is corrected with a strong bias in the direction of the unbroken strand.

scholarly journals Fbh1 Limits Rad51-Dependent Recombination at Blocked Replication Forks

2009 ◽  
Vol 29 (17) ◽  
pp. 4742-4756 ◽  
Author(s):  
Alexander Lorenz ◽  
Fekret Osman ◽  
Victoria Folkyte ◽  
Sevil Sofueva ◽  
Matthew C. Whitby
Keyword(s):  
Homologous Recombination ◽  
Gene Conversion ◽  
Replication Fork ◽  
Direct Repeat ◽  
Dna Helicase ◽  
Replication Forks ◽  
Site Specific ◽  
Replicative Stress ◽  
Recombinant Formation ◽  
A Site

ABSTRACT Controlling the loading of Rad51 onto DNA is important for governing when and how homologous recombination is used. Here we use a combination of genetic assays and indirect immunofluorescence to show that the F-box DNA helicase (Fbh1) functions in direct opposition to the Rad52 orthologue Rad22 to curb Rad51 loading onto DNA in fission yeast. Surprisingly, this activity is unnecessary for limiting spontaneous direct-repeat recombination. Instead it appears to play an important role in preventing recombination when replication forks are blocked and/or broken. When overexpressed, Fbh1 specifically reduces replication fork block-induced recombination, as well as the number of Rad51 nuclear foci that are induced by replicative stress. These abilities are dependent on its DNA helicase/translocase activity, suggesting that Fbh1 exerts its control on recombination by acting as a Rad51 disruptase. In accord with this, overexpression of Fbh1 also suppresses the high levels of recombinant formation and Rad51 accumulation at a site-specific replication fork barrier in a strain lacking the Rad51 disruptase Srs2. Similarly overexpression of Srs2 suppresses replication fork block-induced gene conversion events in an fbh1Δ mutant, although an inability to suppress deletion events suggests that Fbh1 has a distinct functionality, which is not readily substituted by Srs2.

scholarly journals Genetic Requirements for RAD51- andRAD54-Independent Break-Induced Replication Repair of a Chromosomal Double-Strand Break

2001 ◽  
Vol 21 (6) ◽  
pp. 2048-2056 ◽  
Author(s):  
Laurence Signon ◽  
Anna Malkova ◽  
Maria L. Naylor ◽  
Hannah Klein ◽  
James E. Haber
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Homologous Recombination ◽  
Gene Conversion ◽  
Strand Break ◽  
Double Strand Break ◽  
Telomere Maintenance ◽  
Diploid Cells ◽  
Break Induced Replication ◽  
In Cells

ABSTRACT Broken chromosomes can be repaired by several homologous recombination mechanisms, including gene conversion and break-induced replication (BIR). In Saccharomyces cerevisiae, an HO endonuclease-induced double-strand break (DSB) is normally repaired by gene conversion. Previously, we have shown that in the absence ofRAD52, repair is nearly absent and diploid cells lose the broken chromosome; however, in cells lacking RAD51, gene conversion is absent but cells can repair the DSB by BIR. We now report that gene conversion is also abolished when RAD54, RAD55, and RAD57 are deleted but BIR occurs, as withrad51Δ cells. DSB-induced gene conversion is not significantly affected when RAD50, RAD59, TID1(RDH54), SRS2, or SGS1 is deleted. Various double mutations largely eliminate both gene conversion and BIR, including rad51Δ rad50Δ, rad51Δ rad59Δ, andrad54Δ tid1Δ. These results demonstrate that there is aRAD51- and RAD54-independent BIR pathway that requires RAD59, TID1, RAD50, and presumablyMRE11 and XRS2. The similar genetic requirements for BIR and telomere maintenance in the absence of telomerase also suggest that these two processes proceed by similar mechanisms.

Conservative intrachromosomal recombination between inverted repeats in mouse cells: association between reciprocal exchange and gene conversion.

Genetics ◽  
1988 ◽  
Vol 119 (1) ◽  
pp. 161-169
Author(s):  
R J Bollag ◽  
R M Liskay
Keyword(s):  
Gene Conversion ◽  
Mammalian Cells ◽  
Inverted Repeats ◽  
Intrachromosomal Recombination ◽  
Reciprocal Exchange ◽  
Sequence Inversion ◽  
Mouse Cells ◽  
Simplex Virus ◽  
The Relationship ◽  
Recombination Gene

Abstract Recombination in mammalian cells is thought to involve both reciprocal and nonreciprocal modes of exchange, although rigorous proof is lacking due to the inability to recover all products of an exchange. To investigate further the relationship between these modes of exchange, we have analyzed intrachromosomal recombination between duplicated herpes simplex virus thymidine kinase (HSV tk) mutant alleles arranged as inverted repeats in cultured mouse L cells. In crosses between inverted repeats, a single intrachromatid reciprocal exchange leads to inversion of the sequence between the crossover sites and recovery of both genes involved in the event. The majority of recombinant products do not display such inversion and are thus consistent with a nonreciprocal mode of recombination (gene conversion). The remaining products display the sequence inversion predicted for intrachromatid reciprocal exchange. In light of the fact that intrachromatid exchanges occur, the rarity of intrachromatid double reciprocal exchanges strengthens the interpretation that the majority of events in this and previous investigations involve gene conversion. Furthermore, in accord with prediction, one-third of the reciprocal recombinants (inversions) display associated gene conversion. This association suggests that reciprocal and nonreciprocal modes of exchange are mechanistically related in mammalian cells. Finally, the occurrence of inversion recombinants suggests that intrachromosomal recombination can be a conservative (nondestructive) process.

scholarly journals Chromosomal double-strand breaks induce gene conversion at high frequency in mammalian cells.

1997 ◽  
Vol 17 (11) ◽  
pp. 6386-6393 ◽  
Author(s):  
D G Taghian ◽  
J A Nickoloff
Keyword(s):  
Homologous Recombination ◽  
Gene Conversion ◽  
Mammalian Cells ◽  
Chinese Hamster ◽  
Double Strand Breaks ◽  
Chromosomal Dna ◽  
Exogenous Dna ◽  
Strand Breaks ◽  
Conversion Tract

Double-strand breaks (DSBs) stimulate chromosomal and extrachromosomal recombination and gene targeting. Transcription also stimulates spontaneous recombination by an unknown mechanism. We used Saccharomyces cerevisiae I-SceI to stimulate recombination between neo direct repeats in Chinese hamster ovary (CHO) cell chromosomal DNA. One neo allele was controlled by the dexamethasone-inducible mouse mammary tumor virus promoter and inactivated by an insertion containing an I-SceI site at which DSBs were introduced in vivo. The other neo allele lacked a promoter but carried 12 phenotypically silent single-base mutations that create restriction sites (restriction fragment length polymorphisms). This system allowed us to generate detailed conversion tract spectra for recipient alleles transcribed at high or low levels. Transient in vivo expression of I-SceI increased homologous recombination 2,000- to 10,000-fold, yielding recombinants at frequencies as high as 1%. Strikingly, 97% of these products arose by gene conversion. Most products had short, bidirectional conversion tracts, and in all cases, donor neo alleles (i.e., those not suffering a DSB) remained unchanged, indicating that conversion was fully nonreciprocal. DSBs in exogenous DNA are usually repaired by end joining requiring little or no homology or by nonconservative homologous recombination (single-strand annealing). In contrast, we show that chromosomal DSBs are efficiently repaired via conservative homologous recombination, principally gene conversion without associated crossing over. For DSB-induced events, similar recombination frequencies and conversion tract spectra were found under conditions of low and high transcription. Thus, transcription does not further stimulate DSB-induced recombination, nor does it appear to affect the mechanism(s) by which DSBs induce gene conversion.

scholarly journals Duplication of chickendefensin7gene generated by gene conversion and homologous recombination

2016 ◽  
Vol 113 (48) ◽  
pp. 13815-13820 ◽  
Author(s):  
Mi Ok Lee ◽  
Susanne Bornelöv ◽  
Leif Andersson ◽  
Susan J. Lamont ◽  
Junfeng Chen ◽  
...  
Keyword(s):  
Homologous Recombination ◽  
Copy Number Variation ◽  
Gene Conversion ◽  
Copy Number ◽  
Computational Prediction ◽  
Gene Families ◽  
Duplication Event ◽  
Promoter Regions ◽  
Large Gene ◽  
Number Variation

Defensins constitute an evolutionary conserved family of cationic antimicrobial peptides that play a key role in host innate immune responses to infection. Defensin genes generally reside in complex genomic regions that are prone to structural variation, and defensin genes exhibit extensive copy number variation in humans and in other species. Copy number variation of defensin genes was examined in inbred lines of Leghorn and Fayoumi chickens, and a duplication ofdefensin7was discovered in the Fayoumi breed. Analysis of junction sequences confirmed the occurrence of a simple tandem duplication ofdefensin7with sequence identity at the junction, suggesting nonallelic homologous recombination betweendefensin7anddefensin6. The duplication event generated two chimeric promoters that are best explained by gene conversion followed by homologous recombination. Expression ofdefensin7was not elevated in animals with two genes despite both genes being transcribed in the tissues examined. Computational prediction of promoter regions revealed the presence of several putative transcription factor binding sites generated by the duplication event. These data provide insight into the evolution and possible function of large gene families and specifically, the defensins.

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