DNA polymerase eta contributes to strand bias of mutations of A versus T in immunoglobulin genes

• Published in: The Journal of immunology (1950) 2005-06, Vol.174 (12), p.7781-7786
• Main Authors: Mayorov, Vladimir I, Rogozin, Igor B, Adkison, Linda R, Gearhart, Patricia J
• Format: Article
• Language: English
• Subjects: Adenine Nucleotides - genetics; Amino Acid Motifs - genetics; Base Pairing - genetics; Base Sequence; Clone Cells; DNA Mutational Analysis - methods; DNA-Directed DNA Polymerase - chemistry; DNA-Directed DNA Polymerase - deficiency; DNA-Directed DNA Polymerase - genetics; Gene Rearrangement, B-Lymphocyte, Heavy Chain - genetics; Genes, Immunoglobulin - genetics; Humans; Immunoglobulin Variable Region - genetics; Molecular Sequence Data; Somatic Hypermutation, Immunoglobulin; Substrate Specificity - genetics; Thymine Nucleotides - genetics; Transcription, Genetic; Xeroderma Pigmentosum - enzymology; Xeroderma Pigmentosum - genetics; Xeroderma Pigmentosum - immunology
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.174.12.7781

DNA polymerase (pol) eta participates in hypermutation of A:T bases in Ig genes because humans deficient for the polymerase have fewer substitutions of these bases. To determine whether polymerase eta is also responsible for the well-known preference for mutations of A vs T on the nontranscribed strand, we sequenced variable regions from three patients with xeroderma pigmentosum variant (XP-V) disease, who lack polymerase eta. The frequency of mutations in the intronic region downstream of rearranged J(H)4 gene segments was similar between XP-V and control clones; however, there were fewer mutations of A:T bases and correspondingly more substitutions of C:G bases in the XP-V clones (p < 10(-7)). There was significantly less of a bias for mutations of A compared with T nucleotides in the XP-V clones compared with control clones, whereas the frequencies for mutations of C and G were identical in both groups. An analysis of mutations in the WA sequence motif suggests that polymerase eta generates more mutations of A than T on the nontranscribed strand. This in vivo data from polymerase eta-deficient B cells correlates well with the in vitro specificity of the enzyme. Because polymerase eta inserts more mutations opposite template T than template A, it would generate more substitutions of A on the newly synthesized strand.