Abstract
TLR2 signaling by Mycobacterium tuberculosis 19-kDa lipoprotein (LpqH) inhibits IFN-gamma-induced expression of CIITA by macrophages. Microarray analysis, quantitative RT-PCR, and Western blots showed that LpqH induced C/EBPbeta and C/EBPdelta in kinetic correlation with inhibition of CIITA expression. Of the C/EBPbeta isoforms, liver inhibitory protein (LIP) was notably induced and liver-activating protein was increased by LpqH. Putative C/EBP binding sites were identified in CIITA promoters I and IV (pI and pIV). LpqH induced binding of C/EBPbeta (LIP and liver-activating protein) to biotinylated oligodeoxynucleotide containing the pI or pIV binding sites, and chromatin immunoprecipitation showed that LpqH induced binding of C/EBPbeta and C/EBPdelta to endogenous CIITA pI and pIV. Constitutive expression of C/EBPbeta LIP inhibited IFN-gamma-induced CIITA expression in transfected cells. In summary, LpqH induced expression of C/EBPbeta and C/EBPdelta, and their binding to CIITA pI and pIV, in correlation with inhibition of IFN-gamma-induced expression of CIITA in macrophages, suggesting a role for C/EBP as a novel regulator of CIITA expression.