Somatic hypermutation and gene conversion. (A) Map of Igλ locus in ΦV− AIDR2 cells. TATA box, and VJ and C exons are shown. Double arrow represents the area amplified for sequencing. (B) SHM. Left graph; flow cytometry analysis of 3 sh-control (gray) or 9 sh-Top1 (red) independent clones, with 24–36 subclones analyzed per clone. P value, unpaired two-tailed Student’s t test. Right table; sequence analysis from 10 sh-control and 11 sh-Top1 subclones. P value, unpaired two-tailed Student’s t test. (C) Map of Igλ locus in AID+/+ cells. Yellow boxes represent the position of VJ and C exons, and black boxes show the position of V pseudogenes. Double arrow indicates the region sequenced. (D) GC. Left graph; flow cytometry analysis using 2 sh-control (gray) or 4 sh-Top1 (red) independent clones, with 24 subclones analyzed per clone. P value, unpaired two-tailed Student’s t test. Right table; sequence analysis from 4 sh-control and 8 sh-Top1 subclones. P value, unpaired two-tailed Student’s t test.