hnRNPL-CstF64 complex: coordinating CSR and LSR in IgH locus recombination dynamics through eRNA and NHEJ regulation

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Class switch recombination (CSR) and locus suicide recombination (LSR) are crucial for antibody diversification.
• These processes are initiated by activation-induced cytidine deaminase, creating DNA double-strand breaks (DSBs) in the immunoglobulin heavy chain (IgH) locus.
• Enhancer RNAs (eRNAs) and regulatory regions like the 3' regulatory region (3'RR) are known to be involved in CSR regulation.

Purpose of the Study:

• To identify novel regulators of CSR and LSR.
• To elucidate the mechanism by which heterogeneous ribonucleoprotein L (hnRNPL) influences these recombination processes.
• To understand the link between eRNA transcription and DNA repair in antibody diversification.

Main Methods:

• Investigated the role of hnRNPL in CSR and LSR.
• Analyzed the formation of an eRNA-associated complex involving hnRNPL and CstF64.
• Examined the impact of this complex on RNA polymerase II elongation, eRNA transcription, and DNA repair pathways (NHEJ).
• Assessed the recruitment of DNA repair factors like 53BP1 and Ku80.

Main Results:

• hnRNPL forms a complex with CstF64, a polyadenylation factor.
• This complex enhances RNA polymerase II elongation and eRNA transcription at the 3'RR.
• The hnRNPL/CstF64 complex promotes NHEJ-mediated DNA repair at switch (S) regions and the 3'RR.
• Facilitates the recruitment of 53BP1 and Ku80, impacting CSR and LSR efficiency.

Conclusions:

• hnRNPL is a novel regulator of CSR and LSR.
• The hnRNPL/CstF64 complex integrates eRNA transcription with DNA repair mechanisms.
• This finding reveals a multimodal regulatory network critical for antibody diversification.