Recombination may occur in the absence of transcription in the immunoglobulin heavy chain recombination centre.

ABSTRACT: Developing B cells undergo V(D)J recombination to generate a vast repertoire of Ig molecules. V(D)J recombination is initiated by the RAG1/RAG2 complex in recombination centres (RCs), where gene segments become accessible to the complex. Whether transcription is the causal factor of accessibility or whether it is a side product of other processes that generate accessibility remains a controversial issue. At the IgH locus, V(D)J recombination is controlled by E? enhancer, which directs the transcriptional, epigenetic and recombinational events in the IgH RC. Deletion of E? enhancer affects both transcription and recombination, making it difficult to conclude if E? controls the two processes through the same or different mechanisms. By using a mouse line carrying a CpG-rich sequence upstream of E? enhancer and analyzing transcription and recombination at the single-cell level, we found that recombination could occur in the RC in the absence of detectable transcription, suggesting that E? controls transcription and recombination through distinct mechanisms. Moreover, while the normally E?-dependent transcription and demethylating activities were impaired, recruitment of chromatin remodeling complexes was unaffected. RAG1 was efficiently recruited, thus compensating for the defective transcription-associated recruitment of RAG2, and providing a mechanistic basis for RAG1/RAG2 assembly to initiate V(D)J recombination.

SUBMITTER: Oudinet C 

PROVIDER: S-EPMC7144927 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature