Escherichia coli sbcC mutants permit stable propagation of DNA replicons containing a long palindrome

Recombinant DNA libraries generated in vitro should in theory contain all of the sequences of the genomes from which they are derived. However, the literature is dotted with reports of sequences that cannot be recovered, are under-represented, or are highly unstable. In particular, long palindromic nucleotide sequences of perfect or near-perfect symmetry are either lethal to the vector or suffer deletions or other rearrangements that remove symmetry [Collins, Cold Spring Harbor Symp. Quant. Biol. 45 (1981) 409-416; Collins et al., Gene 19 (1982) 139-146; Hagan and Warren, Gene 24 (1983) 317-326]. We report here that mutation of a single gene, namely sbcC, can overcome this inviability and allow for the stable propagation of a 571-bp nearly perfect palindrome in Escherichia coli. This has implications for the choice of strains used for the recovery and analysis of cloned nucleotide sequences.