Non-consensus heptamer sequences destabilize the RAG post-cleavage complex, making ends available to alternative DNA repair pathways.
V(D)J recombination entails double-stranded DNA cleavage at the antigen receptor loci by the RAG1/2 proteins, which recognize conserved recombination signal sequences (RSSs) adjoining variable (V), diversity (D) and joining (J) gene segments. After cleavage, RAG1/2 remain associated with the coding and signal ends (SE) in a post-cleavage complex (PCC), which is critical for their proper joining by classical non-homologous end joining (NHEJ). Certain mutations in RAG1/2 destabilize the PCC, allowing DNA ends to access inappropriate repair pathways such as alternative NHEJ, an error-prone pathway implicated in chromosomal translocations. The PCC is thus thought to discourage aberrant rearrangements by controlling repair pathway choice. Since interactions between RAG1/2 and the RSS heptamer element are especially important in forming the RAG-SE complex, we hypothesized that non-consensus heptamer sequences might affect PCC stability. We find that certain non-consensus heptamers, including a cryptic heptamer implicated in oncogenic chromosomal rearrangements, destabilize the PCC, allowing coding and SEs to be repaired by non-standard pathways, including alternative NHEJ. These data suggest that some non-consensus RSS, frequently present at chromosomal translocations in lymphoid neoplasms, may promote genomic instability by a novel mechanism, disabling the PCC's ability to restrict repair pathway choice.
Department of Pathology, New York University School of Medicine, New York, NY 10016, USA.
Suzzette M
SM
Arnal
Abigail J
AJ
Holub
Sandra S
SS
Salus
David B
DB
Roth
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000737:chemistry; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D056426:Genetic Loci; D042822:Genomic Instability; D018398:Homeodomain Proteins / Q000378:metabolism*; D009711:Nucleotides / Q000032:analysis; D011995:Recombination, Genetic
D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D009711:Nucleotides; C064655:V(D)J recombination activating protein 2; C064658:RAG-1 protein; D004247:DNA