Role for DNA polymerase κ in the processing of N²-N ²-guanine interstrand cross-links

Although there exists compelling genetic evidence for a homologous recombination-independent pathway for repair of interstrand cross-links (ICLs) involving translesion synthesis (TLS), biochemical support for this model is lacking. To identify DNA polymerases that may function in TLS past ICLs, oligodeoxynucleotides were synthesized containing site-specific ICLs in which the linkage was between N²-guanines, similar to crosslinks formed by mitomycin C and enals. Here, data are presented that mammalian cell replication of DNAs containing these lesions was ∼97% accurate. Using a series of oligodeoxynucleotides that mimic potential intermediates in ICL repair, we demonstrate that human polymerase (pol) κ not only catalyzed accurate incorporation opposite the cross-linked guanine but also replicated beyond the lesion, thus providing the first biochemical evidence for TLS past an ICL. The efficiency of TLS was greatly enhanced by truncation of both the 5′ and 3′ ends of the nontemplating strand. Further analyses showed that although yeast Rev1 could incorporate a dCTP opposite the cross-linked guanine, no evidence was found for TLS by pol ζ or a polζ/Rev1 combination. Because pol κ was able to bypass these ICLs, biological evidence for a role for pol κ in tolerating the N²-N²-guanine ICLs was sought; both cell survival and chromosomal stability were adversely affected in pol κ-depleted cells following mitomycin C exposure. Thus, biochemical data and cellular studies both suggest a role for pol κ in the processing of N²-N²-guanine ICLs.