Figure 5.

DNA strand polarity of switch-associated mutations in LPS-cultured B cells. (A) DNA strand polarity of C→T transition mutations in individual S region sequences amplified from splenic B cells from msh2 ^−/− ung ^−/− mice at day 7 of culture with LPS+IL-4/IFN-γ. (B) DNA strand polarity of C→T transition mutations in individual Sμ m.2 sequences amplified from splenic B cells from msh2 ^−/− ung ^−/− mice at day 5 of culture with LPS+IL-4/IFN-γ. All mutated sequences are illustrated with C→T transitions on the transcription template strand indicated by open circles below the line; those on the nontemplate strand are indicated by closed circles above the line. Asterisks mark sequences that harbor tandem C→T transitions on one strand in regions where other sequences in the database exhibit mutations on the opposite strand. Clusters of same DNA strand (linked) mutations were quantified by scoring the frequency of “same” (AA to TT) contiguous mutations (ignoring intervening distance) compared with the frequency of “different” (AT or TA) contiguous mutations in each sequence obtained from LPS-stimulated B cells. The bias in favor of same strand mutations was estimated using a χ² test (P = 0.0277).