The recombination initiation functions DprA and RecFOR suppress
microindel mutations in Acinetobacter baylyi ADP1
Abstract
Short-Patch Double Illegitimate Recombination (SPDIR) has been recently
identified as a rare mutation mechanism. During SPDIR, ectopic DNA
single-strands anneal with genomic DNA at microhomologies and get
integrated in the course of DNA replication, presumably acting as
Okazaki fragments. The resulting microindel mutations are highly
variable in size and sequence. In the soil bacterium Acinetobacter
baylyi, SPDIR mutations are tightly controlled by genome maintenance
functions including RecA. In this study, we investigate the roles of
DprA, RecFOR and RecBCD, which are cytoplasmic functions that load DNA
single-strands with RecA. All three functions suppress SPDIR mutations
in wildtype to levels below the detection limit. While SPDIR mutations
are slightly elevated in the absence of DprA alone, they are strongly
increased in the absence of both DprA and RecA. This SPDIR-avoiding
function of DprA is not related to its role in natural transformation.
These results suggest an antimutational function for DprA and offer an
explanation for the ubiquity of dprA in the genomes of
non-transformable bacteria.