Genome sequence and splice site analysis of low-fidelity DNA polymerases H and I involved in replication of damaged DNA.

POLH and POLI are paralogs encoding low-fidelity, class Y, DNA polymerases involved in replication of damaged DNA in the human disease xeroderma pigmentosum variant. Analysis of genomic regions for human and mouse homologs, employing the analytic tool Genome Cryptographer, detected low-repetitive or unique regions at exons and other potential control regions, especially within intron I of human POLH. The human and mouse homologs are structurally similar, but the paralogs have undergone evolutionary divergence. The information content of splice sites for human POLH, the probability that a base would contribute to splicing, was low only for the acceptor site of exon II, which is preceded by a region of high information content that could contain sequences controlling splicing. This analysis explains previous observations of tissue-specific skipping during mRNA processing, resulting in the loss of the transcription start site in exon II, in human tissues.