Abstract
Pax5, a member of the paired box gene family of transcription factors, is a B cell‐specific activator protein (BSAP) that plays important roles in controlling the expression of lineage‐ and differentiation‐stage specific genes during B lymphopoiesis. We identified two putative Pax5 binding sites in a 668 bp of the murine 1‐cys peroxiredoxin (1‐cysPrx) promoter region. These sites were located at positions −278 to −262 and −50 to −34 from the translation start site. Gel mobility shift assays showed that recombinant Pax5 protein bound specifically to the nucleotide regions −56 to −24 (MP1 probe) and −284 to −253 (MP2 probe). Furthermore, endogenous Pax5 protein from B lymphoblast cells (IM‐9) formed a DNA‐protein complex with MP1 and MP2 probes, indicating that Pax5 binding occurs specifically at these sequences in vivo. Transient transfection studies showed that expression of exogenous Pax5 resulted in dose‐dependent increases in 1‐cysPrx promoter activity, implying that Pax5 functions as a positive transcription factor for 1‐cysPrx expression. Further transient cotransfection studies showed that coexpression of Pax5 and histone acetyltransferases (HATs), such as p300, cAMP‐response‐element‐binding protein (CBP) and p300/CBP associated factor (PCAF) enhanced the Pax5‐mediated 1‐cysPrx promoter activity. Immunoprecipitation studies indicated that Pax5 directly binds to HATs. Chromatin immunoprecipitation assays showed that the recruitment of Pax5 to the promoter induced histone H3 and H4 hyperacetylation of chromatin. Lipopolysaccharides (LPS) stimulation of murine splenocytes resulted in coordinated expression of Pax5 and 1‐cysPrx proteins. These findings suggest that Pax5 may function as a transactivator of 1‐cysPrx gene expression. J. Cell. Biochem. 104: 465–476, 2008. © 2008 Wiley‐Liss, Inc.