Probing immunoglobulin gene hypermutation with microsatellites suggests a nonreplicative short patch DNA synthesis process.
As the rate of Ig gene hypermutation approximates the level of nucleotide discrimination of DNA polymerases (10(-3) to 10(-4)), a local inhibition of proofreading and mismatch repair during semiconservative replication could generate the mutations introduced by the process. To address this question, we have constructed transgenic mice that carry a hypermutation substrate containing a "polymerase slippage trap": an Ig gene with a mono or dinucleotide tract inserted in its V region. The low amount of slippage events as compared to the number of mutations, the absence of transient misalignment mutations at the border of the repeats, and the dissociation between the amount of frameshifts and mutations when the transgene is put on mismatch repair-deficient genetic backgrounds, suggest that Ig gene hypermutation occurs by an error-prone short patch DNA synthesis taking place outside global DNA replication.
Bertocci
B
B
INSERM U 373, Faculté de Médecine Necker-Enfants Malades, Paris, France.
Quint
L
L
Delbos
F
F
Garcia
C
C
Reynaud
C A
CA
Weill
J C
JC
D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology; D004247:DNA / Q000096:biosynthesis*; D015342:DNA Probes / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics; D004261:DNA Replication / Q000235:genetics*; D004259:DNA-Directed DNA Polymerase; D016368:Frameshift Mutation / Q000235:genetics; D005803:Genes, Immunoglobulin / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics; D007145:Immunoglobulin kappa-Chains / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008822:Mice, Transgenic; D018895:Microsatellite Repeats / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D010581:Peyer's Patches / Q000166:cytology; D013997:Time Factors; D019076:Transgenes / Q000235:genetics
D015342:DNA Probes; D007135:Immunoglobulin Variable Region; D007145:Immunoglobulin kappa-Chains; D004247:DNA; D004259:DNA-Directed DNA Polymerase