Sequence analysis of clonal LCLs derived from EBV-infected BCR- B cells. The sequences of 4 single-cell LCL clones are shown, which carry a crippled heavy chain allele and fail to express a functional BCR. A detailed comparison of VDJH gene regions of the 4 sequenced clones (bottom lines) to the most homologous germ line genes (top lines) is shown. Sequence identity is indicated by dashes, and nucleotide exchanges introduced by somatic hypermutation are indicated. Uppercase characters denote replacement mutations, and lowercase characters describe silent mutations. (A) In clone A54 an in-frame stop codon (marked with asterisks) in CDR1 (solid lines) abrogates HC expression. (B) In clone A16 only the variable and the joining segment could be determined, since this rearranged heavy chain allele suffers from a massive internal deletion, which is indicated by boxes. The deletion also causes a frame shift mutation such that the C segments are out of phase. The clones B5 (C) and B11 (D) are crippled due to in-frame stop codons (asterisks). The forward and backward primer binding sites (dotted lines) contain wobbled bases: M (adenosine or a cytidine), and Y (cytidine or a thymidine).
