[show abstract][hide abstract] ABSTRACT: RAG1 and RAG2 play a central role in V(D)J recombination, a process for antigen receptor gene assembly. The truncated 'core' regions of RAGs are sufficient to catalyze the recombination reaction, although with lower joining efficiency than full-length proteins. To investigate the role of the non-core regions of RAGs in the end-joining phase of antigen receptor rearrangement, we analyzed recombination products isolated from core RAG1 and core RAG2 knock-in mice. Here, we report that the truncation of RAGs increases the frequency of aberrant recombination in vivo. Signal joints (SJs) associated with V-to-D recombination of core RAG1 knock-in mice were normal, whereas those of core RAG2 knock-in mice were highly imprecise, containing large deletions and additions, and in some cases coding sequences. In contrast, we found an elevated level of imprecise D-to-J associated SJs for both core RAG1- and RAG2-expressing mice. Likewise, sequences of coding joints (CJs) were also affected by the expression of core RAGs. Finally, sequences found at the junctions of rearranged T-cell receptor loci were highly influenced by differences in rearranging recombination signal sequence pairs. We provide the first evidence that the non-core regions of RAGs have critical functions in the proper assembly and resolution of recombination intermediates in endogenous antigen receptor loci.
Nucleic Acids Research 02/2004; 32(15):4539-49. · 8.28 Impact Factor
[show abstract][hide abstract] ABSTRACT: It has been suggested that DNA methylation/demethylation is involved in regulating V(D)J rearrangement. Although methylated DNA is thought to induce an inaccessible chromatin structure, it is unclear whether DNA methylation can directly control V(D)J recombination independently of chromatin structure. In this study, we tested whether DNA methylation directly affects the reactivity of the RAG1/RAG2 complex. Specific methylation within the heptamer of the recombination signal sequences (RSS) markedly reduced V(D)J cleavage without inhibiting RAG1/RAG2-DNA complex formation. By contrast, methylation at other positions around the RSS did not affect the reactivity of the RAG proteins. The presence of a methyl-CpG binding-domain protein inhibited the binding of the RAG1/RAG2 complex to all the methylated CpG sites that were tested. Our findings suggest that DNA methylation around the RSS may have a previously unexpected function in regulating V(D)J recombination by directly inhibiting V(D)J cleavage, in addition to its general function of inducing an inaccessible chromatin configuration.
[show abstract][hide abstract] ABSTRACT: The recombination-activating gene (RAG)1 and RAG2 proteins comprise the lymphocyte-specific components of the V(D)J recombinase and are required for the assembly of antigen-receptor variable-region genes. A mutant truncated RAG2 protein ("core" RAG2) lacking the C-terminal 144 amino acids, together with core RAG1, is able to mediate the basic biochemical steps required for V(D)J recombination in vitro and in transfected cell lines. Here we examine the effect of replacing the endogenous RAG2 locus in mice with core RAG2. These mice generate substantial numbers of B and T cells, demonstrating that the core RAG2 protein retains significant in vivo function. However, core RAG2 mice display a reduction in the total number of B and T cells, reflecting impaired lymphocyte development at the progenitor stage associated with reduced chromosomal V(D)J recombination. We discuss potential roles of the RAG2 C terminus in mediating rearrangement of endogenous antigen-receptor loci.
Proceedings of the National Academy of Sciences 03/2003; 100(3):1209-14. · 9.74 Impact Factor