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During infection of macrophages, prolonged signaling by Mycobacterium tuberculosis (Mtb) or its 19-kDa lipoprotein (LpqH; Rv3763) inhibits IFN-γ-induced expression of several immune function genes, including class II transactivator (CIITA), which regulates class II MHC. Mtb does not inhibit early IFN-γ signaling events, eg, Stat1α activation. This study analyzed downstream mechanisms that regulate the transcription of MHC2TA, the gene encoding CIITA. Chromatin immunoprecipitation showed that IFN-γ induced acetylation of histones H3 and H4 at the CIITA promoter IV (pIV). In contrast, IFN-γ-dependent histone acetylation at CIITA pIV was inhibited by Mtb or 19-kDa lipoprotein. Mtb 19-kDa lipoprotein also inhibited IFN-γ-dependent recruitment of Brahma-related gene 1, a chromatin remodeling protein, to CIITA pIV. Mtb 19-kDa lipoprotein did not inhibit histone acetylation in TLR2−/− macrophages. Furthermore …