INTERDEPENDENCE OF N NUCLEOTIDE ADDITION AND RECOMBINATION SITE CHOICE IN V(D)J REARRANGEMENT

Diversity in the Ag binding receptors of B and T cells is achieved thr ough a process of genomic rearrangement involving selection of recombi nation sites and, in adult mice, addition of nontemplated (N) nucleoti des, We have analyzed 543 Ig heavy chain nonproductive rearrangements, involving a single variable region gene segment, from adult and perin atal mice. We infer several fundamental and novel features of the reco mbination mechanism, N regions are formed predominantly from the DNA p lus strand or from the DNA minus strand polymerizations, rather than a s a concatenation of the two, Homologous overlaps of as few as one nuc leotide between gene segments cause significant skewing of recombinati on sites, The V-H recombination site spectrum differs in perinatal and adult mice, with sites representing overlap between V-H and D over-re presented in the perinatal mice, and sites representing overlaps betwe en V-H and the N strand polymerized onto the D segment over-represente d in the adult mice, Thus, in V(D)J joining, N nucleotide addition and recombination site choice are highly interdependent events.