RT Journal Article SR Electronic T1 Chromosomal Lesion Suppression and Removal in Escherichia coli via Linear DNA Degradation JF Genetics JO Genetics FD Genetics Society of America SP 1255 OP 1271 VO 163 IS 4 A1 Miranda, Anabel A1 Kuzminov, Andrei YR 2003 UL http://www.genetics.org/content/163/4/1255.abstract AB RecBCD is a DNA helicase/exonuclease implicated in degradation of foreign linear DNA and in RecA-dependent recombinational repair of chromosomal lesions in E. coli. The low viability of recA recBC mutants vs. recA mutants indicates the existence of RecA-independent roles for RecBCD. To distinguish among possible RecA-independent roles of the RecBCD enzyme in replication, repair, and DNA degradation, we introduced wild-type and mutant combinations of the recBCD chromosomal region on a low-copy-number plasmid into a ΔrecA ΔrecBCD mutant and determined the viability of resulting strains. Our results argue against ideas that RecBCD is a structural element in the replication factory or is involved in RecA-independent repair of chromosomal lesions. We found that RecBCD-catalyzed DNA degradation is the only activity important for the recA-independent viability, suggesting that degradation of linear tails of σ-replicating chromosomes could be one of the RecBCD’s roles. However, since the weaker DNA degradation capacity due a combination of the RecBC helicase and ssDNA-specific exonucleases restores viability of the ΔrecA ΔrecBCD mutant to a significant extent, we favor suppression of chromosomal lesions via linear DNA degradation at reversed replication forks as the major RecA-independent role of the RecBCD enzyme.