Impact of acetyltransferases in B cell development
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AbstractHistone acetylation is a crucial mechanism involved in several cellular functions, including embryogenesis, DNA repair, cell cycle regulation, neurogenesis, and lymphocyte development. Acetyltransferases are the key modulators, which mediate the acetylation of the histone and non-histone proteins associated with an array of cellular mechanisms. General control non-derepressible 5 (Gcn5) and p300/CBP-associated factor (PCAF) are homologous acetyltransferases from the GNAT family, which take up the major regulatory role in cellular functions as transcription activators and DNA damage response factors. Furthermore, several studies have substantiated their intricate part in lymphocyte development. However, the contribution of Gcn5 and PCAF in one of the B cell developmental stages, the class switch recombination, remains unappreciated. Here, both the proteins, Gcn5 and PCAF were catalytically inactivated by specific inhibitor, CPTH2, and genetically attenuated using the CRISPR/Cas9 gene-editing approach in CH12F3 cells, to assess the impact of the proteins in CSR. Interestingly, loss of Gcn5 and PCAF in CH12F3 cells by both the strategies showed profound impairment in IgA isotype switching and nearly four-fold reduction in the CSR was observed, suggesting that Gcn5 and PCAF are indispensable factors in CSR.H3K9 acetylation is a hallmark of active genes. The key enzymes engaged in H3K9 acetylation in the cells are Gcn5 and PCAF. Contrastingly, the H3K9ac of pre-B cells is not mediated by Gcn5 and PCAF during B lymphogenesis. The acetyltransferases, p300, and CBP physically bind to an acetylated PCAF. In addition, p300 shares early developmental functions with Gcn5 during embryogenesis. To determine whether the proteins p300 and CBP compensate the function of Gcn5/PCAF in pre-B cells, the vAbl cells were treated with distinct concentrations of specific inhibitor, PU139, which blocks the catalytic activity of Gcn5, PCAF, p300, and CBP. No significant acetylation inhibition was observed after the inhibitory treatment. This result suggests H3K9ac in pre-B cells is not orchestrated by p300 and CBP.