Histone acetyltransferase PCAF is involved in transactivation of Bcl-6 and Pax5 genes in immature B cells.

Histone acetyltransferase p300/CBP-associated factor (PCAF) belonging to GCN5 family regulates various epigenetic events for transcriptional regulation through alterations in the chromatin structure. During normal development of B cells, gene expressions of numerous transcription factors are strictly regulated by epigenetic mechanisms including histone acetylation and deacetylation to complete their development pathways. Here, by analyzing PCAF-deficient DT40 mutants, ΔPCAF, we report that PCAF takes part in transcriptional activation of B cell lymphoma-6 (Bcl-6) and Paired box gene 5 (Pax5), which are essential transcription factors for normal development of B cells. PCAF-deficiency caused drastic decrease in mRNA levels of Bcl-6 and Pax5, and remarkable increase in that of B lymphocyte-induced maturation protein-1 (Blimp-1). In addition, chromatin immunoprecipitation assay showed that PCAF-deficiency caused remarkable decrease in acetylation levels of both H3K9 and H3K14 residues within chromatin surrounding the 5'-flanking regions of Bcl-6 and Pax5 genes in vivo, suggesting that their gene expressions may be regulated by PCAF. These results revealed that PCAF is involved in transactivation of Bcl-6 and Pax5 genes, resulting in down-regulation of Blimp-1 gene expression, and plays a key role in epigenetic regulation of B cell development.