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Figure S2. Sμ–Sγ3 microhomology length is similar in WT and DBL mice. Closed squares represent microhomology between donor/acceptor sequences. Sμ–Sγ3 junctions were amplified from B cells stimulated with LPS plus anti–δ-dextran for 4 d. WT and DBL mice were not significantly different (P = 0.0646 according to the Mann-Whitney U t test). Genomic DNA was isolated from cultured B cells by incubation with 0.5 mg/ml proteinase K, 100 μg/ml RNaseA, and 0.5% SDS in STE (0.1M NaCl, 20 mM Tris [pH 8], 1 mM EDTA) for 2 h at 37°C, followed by three to four extractions with phenol/chloroform (1:1) and precipitation with 0.3 M sodium acetate, pH 7, and ethanol. DNA was wound out on glass rods and resuspended in TE, pH 8. Sμ–Sγ3 junctions were amplified by PCR using Expand Long Template Taq polymerase (Roche) and the primers μ3-H3 (5′-AACAAGCTTGGCTTAACCGAGATGAGCC-3′) and g3-2 (5′-TACCCTGACCCAGGAGCTGCATAAC-3′; MUSIGHANA, nt 2603–2628). PCR products were cloned into the vector pCR4-TOPO (Invitrogen) and sequenced by Macrogen using T3 and T7 primers. For the sequence analyses, the WT sequences from the corresponding littermates were used. Sequences with insertions at the Sμ–Sγ3 junctions were scored as having no microhomology.