Mouse kappa light-chain recombination signal sequences mediate recombination more frequently than do those of lambda light chain.

Abstract

Immunoglobulin and T-cell receptor genes are somatically rearranged by site-specific recombination. Recombination signal sequences (RSS) have been identified as the major targeting element of this process. Recent reports demonstrate that differences in RSS affect the frequency of recombination, suggesting a role for RSS in the development of the B-cell repertoire. Examination of mouse light-chain RSS indicates that kappa light-chain RSS consistently show a greater degree of similarity to a consensus sequence than do those of lambda light chain. To determine whether this difference in natural RSS could affect the patterns of light-chain gene rearrangement and expression, we have constructed recombination substrates containing both a typical mouse kappa RSS pair and a typical mouse lambda RSS pair. Experiments using these substrates demonstrate that the kappa RSS pair mediates recombination at a vastly higher frequency than does the lambda RSS pair. This result argues that RSS differences may contribute significantly to the patterns of mouse immunoglobulin light-chain rearrangement, ultimately resulting in a high proportion of kappa light chain relative to lambda.

Targets of somatic hypermutation within immunoglobulin light chain genes in zebrafish

“…Our decision to target an IgL locus with a canonical recombination signal sequences (RSS) was made on the assumption that such a locus would be likely to yield the highest number of transcripts. This assumption is supported by previous work by Ramsden and Wu, 8 who found that synthetic substrates of mouse origin showed favoured expression of V segments flanked by RSS that more closely resemble canonical heptamer (CACAGTG) and nonamer (ACAAACC) sequences. By focusing on a single rearranged IgL gene (V7) and constructing an enriched cDNA library from a single individual, direct comparison of sequences could be utilized to discern mutational hotspots and potential lineages of clonal expansions could be examined.…”

A Change in the Structure of Vβ Chromatin Associated with TCR β Allelic Exclusion

“…We note as well that accessibility is clearly not the only factor governing RAG cleavage in chromatin. Sequence variation among natural RSS heptamer and nonamers (58,59), spacer regions (60), and coding flanks (61-64) can significantly impact rearrangement frequencies as well. It is notable that V␤12, which is inaccessible in the DP compartment, carries a nonamer (GCAAAAACA) that diverges from the consensus (ACAAAAACC) at only the end positions.…”

Unequal VH Gene Rearrangement Frequency Within the Large VH7183 Gene Family Is Not Due to Recombination Signal Sequence Variation, and Mapping of the Genes Shows a Bias of Rearrangement Based on Chromosomal Location

“…Previously we and others have found a strong correlation between the relative frequency of rearrangement of genes in vivo and the ability of their RSS to support recombination in vitro in recombination substrates. In some cases different loci (e.g., vs ) or different genes within a locus (e.g., the three VIII genes) were analyzed, so the correlation could possibly be deemed coincidental (18,19). However, for the VA2 genes we showed that two alleles differing at one position in the heptamer rearrange at ϳ5-fold different frequencies in vivo and in vitro, and the alleles presumably are identical in chromosomal location and sequence (only three changes were found in 700 bp) strongly suggesting that indeed the RSS was responsible for the differences in rearrangement frequencies in vivo vs in vitro (21).…”

“…We also identified a second new, apparently functional, gene that we have provisionally called 7183. 19 (24). Therefore, this RSS is highly likely to be nonfunctional.…”