The recombination hot spot chi is embedded within islands of preferred DNA pairing sequences in the E. coli genome.
Published in Cell
The BRC repeats of BRCA2 modulate the DNA-binding selectivity of RAD51.
Published in Cell
The breast cancer susceptibility protein, BRCA2, is essential for recombinational DNA repair. BRCA2 delivers RAD51 to double-stranded DNA (dsDNA) breaks through interaction with eight conserved, approximately 35 amino acid motifs, the BRC repeats. Here we show that the solitary BRC4 promotes assembly of RAD51 onto single-stranded DNA (ssDNA), but n...
A molecular throttle: the recombination hotspot chi controls DNA translocation by the RecBCD helicase.
Published in Cell
RecBCD enzyme is a heterotrimeric helicase/nuclease that initiates homologous recombination at double-stranded DNA breaks. Several of its activities are regulated by the DNA sequence chi (5 -GCTGGTGG-3 ), which is recognized in cis by the translocating enzyme. When RecBCD enzyme encounters chi, the intensity and polarity of its nuclease activity ar...
The translocating RecBCD enzyme stimulates recombination by directing RecA protein onto ssDNA in a chi-regulated manner....
Published in Cell
Double-stranded DNA break repair and homologous recombination in E. coli are initiated by the RecBCD enzyme, which unwinds and simultaneously degrades DNA from a double-stranded DNA end. This process is stimulated by cis-acting DNA elements, known as chi sites. Using both in vitro pairing and nuclease protection assays, we demonstrate that the tran...
The recombination hotspot chi is a regulatory sequence that acts by attenuating the nuclease activity of the E. coli Rec...
Published in Cell
The RecBCD enzyme is a multifunctional enzyme that is essential for homologous recombination in E. coli. In vitro, the RecBCD enzyme degrades linear double-stranded DNA nonspecifically during the process of unwinding the double-stranded DNA. Here we demonstrate that this DNA degradation is asymmetric, with the strand that is 3 terminal at the entr...
Homologous pairing in vitro stimulated by the recombination hotspot, Chi.
Published in Cell
Genetic recombination in Escherichia coli is stimulated at DNA sequences known as Chi sites, 5 -GCT-GGTGG-3 . We describe the in vitro formation of homologously paired joint molecules that is dependent upon this recombination hotspot. Chi-dependent joint molecule formation requires RecA, RecBCD, and SSB proteins and a Chi site in the donor linear d...
Reconstitution of an SOS response pathway: derepression of transcription in response to DNA breaks.
Published in Cell
E. coli responds to DNA damage by derepressing the transcription of about 20 genes that make up the SOS pathway. Genetic analyses have shown that SOS induction in response to double-stranded DNA (dsDNA) breaks requires LexA repressor, and the RecA and RecBCD enzymes—proteins best known for their role as initiators of dsDNA break repair and homologo...
Saccharomyces cerevisiae Mer3 helicase stimulates 3 -5 heteroduplex extension by Rad51; implications for crossover cont...
Published in Cell
Crossover and noncrossover recombinants can form by two different pathways during meiotic recombination in Saccharomyces cerevisiae. The MER3 gene is known to affect selectively crossover, but not noncrossover, recombination. The Mer3 protein is a DNA helicase that unwinds duplex DNA in the 3 to 5 direction. To define the underlying molecular ste...
RecBCD enzyme switches lead motor subunits in response to chi recognition.
Published in Cell
RecBCD is a DNA helicase comprising two motor subunits, RecB and RecD. Recognition of the recombination hotspot, chi, causes RecBCD to pause and reduce translocation speed. To understand this control of translocation, we used single-molecule visualization to compare RecBCD to the RecBCD(K177Q) mutant with a defective RecD motor. RecBCD(K177Q) pause...
