Dynamic O-GlcNAcylation governs long-range chromatin interaction in VDJ recombination during early B cell development

VDJ recombination secures to produce functional immunoglobulin Ig genes and antibody diversity during the early stages of B cell development through long-distance interactions mediated by cisregulatory elements and trans-acting factors. O-GlcNAcylation is a dynamic and reversible post-translational modification of nuclear and cytoplasmic proteins that regulates various protein functions, including DNA binding affinity and protein-protein interactions. However, the effect of O-GlcNAcylation on proteins involved in VDJ recombination remains largely unknown. To elucidate this relationship, we downregulated O-GlcNAcylation in a mouse model by administrating an O-GlcNAc inhibitor or restricting their regular diet. Interestingly, inhibition of O-GlcNAcylation in mice severely impaired Ig heavy chain IgH gene rearrangement. We identified several factors crucial for VDJ recombination, including YY1, CTCF, SMC1 and SMC3, as direct targets of O-GlcNAc modification. Importantly, O-GlcNAcylation regulates the physical interaction between SMC1 and SMC3 and the DNA-binding patterns of YY1 at the IgH gene locus. Moreover, O-GlcNAc inhibition downregulated DDX5 protein expression, affecting the functional association of CTCF with its DNA binding sites on IgH locus. Our results showed that the locus contraction and long-range interactions throughout the IgH locus are disrupted depending on cellular O-GlcNAc levels. In this study, we established that VDJ recombination relies on the O-GlcNAc status of stage specific proteins during early B cell development and represents O-GlcNAc-dependent mechanisms as new regulatory components for developing a diverse antibody repertoire.