Highly mismatch-tolerant homology testing by RecA could explain how homology length affects recombination.
PLoS One
; 18(7): e0288611, 2023.
Article
em En
| MEDLINE
| ID: mdl-37440583
ABSTRACT
In E. coli, double strand breaks (DSBs) are resected and loaded with RecA protein. The genome is then rapidly searched for a sequence that is homologous to the DNA flanking the DSB. Mismatches in homologous partners are rare, suggesting that RecA should rapidly reject mismatched recombination products; however, this is not the case. Decades of work have shown that long lasting recombination products can include many mismatches. In this work, we show that in vitro RecA forms readily observable recombination products when 16% of the bases in the product are mismatched. We also consider various theoretical models of mismatch-tolerant homology testing. The models test homology by comparing the sequences of Ltest bases in two single-stranded DNAs (ssDNA) from the same genome. If the two sequences pass the homology test, the pairing between the two ssDNA becomes permanent. Stringency is the fraction of permanent pairings that join ssDNA from the same positions in the genome. We applied the models to both randomly generated genomes and bacterial genomes. For both randomly generated genomes and bacterial genomes, the models show that if no mismatches are accepted stringency is â¼ 99% when Ltest = 14 bp. For randomly generated genomes, stringency decreases with increasing mismatch tolerance, and stringency improves with increasing Ltest. In contrast, in bacterial genomes when Ltest â¼ 75 bp, stringency is â¼ 99% for both mismatch-intolerant and mismatch-tolerant homology testing. Furthermore, increasing Ltest does not improve stringency because most incorrect pairings join different copies of repeats. In sum, for bacterial genomes highly mismatch tolerant homology testing of 75 bp provides the same stringency as homology testing that rejects all mismatches and testing more than â¼75 base pairs is not useful. Interestingly, in vivo commitment to recombination typically requires homology testing of â¼ 75 bp, consistent with highly mismatch intolerant testing.
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Base de dados:
MEDLINE
Assunto principal:
DNA
/
Escherichia coli
Idioma:
En
Ano de publicação:
2023
Tipo de documento:
Article