TY - JOUR
T1 - Absence of DNA Polymerase η Reveals Targeting of C Mutations on the Nontranscribed Strand in Immunoglobulin Switch Regions
AU - Zeng, Xianmin
AU - Negrete, George A.
AU - Kasmer, Cynthia
AU - Yang, William W.
AU - Gearhart, Patricia J.
PY - 2004/4/5
Y1 - 2004/4/5
N2 - Activation-induced cytosine deaminase preferentially deaminates C in DNA on the nontranscribed strand in vitro, which theoretically should produce a large increase in mutations of C during hypermutation of immunoglobulin genes. However, a bias for C mutations has not been observed among the mutations in variable genes. Therefore, we examined mutations in the μ and γ switch regions, which can form stable secondary structures, to look for C mutations. To further simplify the pattern, mutations were studied in the absence of DNA polymerase (pol) η, which may produce substitutions of nucleotides downstream of C. DNA from lymphocytes of patients with xeroderma pigmentosum variant (XP-V) disease, whose polymerase η is defective, had the same frequency of switching to all four γ isotypes and hypermutation in μ-γ switch sites (0.5% mutations per basepair) as control subjects. There were fewer mutations of A and T bases in the XP-V clones, similar to variable gene mutations from these patients, which confirms that polymerase η produces substitutions opposite A and T. Most importantly, the absence of polymerase η revealed an increase in C mutations on the nontranscribed strand. This data shows for the first time that C is preferentially mutated in vivo and pol η generates hypermutation in the μ and γ switch regions.
AB - Activation-induced cytosine deaminase preferentially deaminates C in DNA on the nontranscribed strand in vitro, which theoretically should produce a large increase in mutations of C during hypermutation of immunoglobulin genes. However, a bias for C mutations has not been observed among the mutations in variable genes. Therefore, we examined mutations in the μ and γ switch regions, which can form stable secondary structures, to look for C mutations. To further simplify the pattern, mutations were studied in the absence of DNA polymerase (pol) η, which may produce substitutions of nucleotides downstream of C. DNA from lymphocytes of patients with xeroderma pigmentosum variant (XP-V) disease, whose polymerase η is defective, had the same frequency of switching to all four γ isotypes and hypermutation in μ-γ switch sites (0.5% mutations per basepair) as control subjects. There were fewer mutations of A and T bases in the XP-V clones, similar to variable gene mutations from these patients, which confirms that polymerase η produces substitutions opposite A and T. Most importantly, the absence of polymerase η revealed an increase in C mutations on the nontranscribed strand. This data shows for the first time that C is preferentially mutated in vivo and pol η generates hypermutation in the μ and γ switch regions.
KW - Activation-induced cytosine deaminase
KW - Gap-filling repair
KW - Somatic hypermutation
KW - Translesion replication
KW - Xeroderma pigmentosum variant
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U2 - 10.1084/jem.20032022
DO - 10.1084/jem.20032022
M3 - Article
C2 - 15051760
AN - SCOPUS:1842732235
VL - 199
SP - 917
EP - 924
JO - Journal of Experimental Medicine
JF - Journal of Experimental Medicine
SN - 0022-1007
IS - 7
ER -