Piskurich Janet F, Gilbert Carolyn A, Ashley Brittany D, Zhao Mojun, Chen Han, Wu Jian, Bolick Sophia C, Wright Kenneth L
Division of Basic Sciences, Mercer University School of Medicine, 1550 College St., Macon, GA 31207, USA.
Mol Immunol. 2006 Feb;43(6):519-28. doi: 10.1016/j.molimm.2005.05.005. Epub 2005 Jun 13.
The MHC class II transactivator (CIITA), the master regulator of MHC class II (MHC II) expression, is a co-activator that controls MHC II transcription. Human B lymphocytes express MHC II constitutively due to persistent activity of CIITA promoter III (pIII), one of the four potential promoters (pI-pIV) of this gene. Although increases in MHC II expression in B cells in response to cytokines have been observed and induction of MHC II and CIITA by IFN-gamma has been studied in a number of different cell types, the specific effects of IFN-gamma on CIITA expression in B cells have not been studied. To investigate the regulation of CIITA expression by IFN-gamma in B cells, RT-PCR, in vivo and in vitro protein/DNA binding studies, and functional promoter analyses were performed. Both MHC II and CIITA type IV-specific RNAs increased in human B lymphocytes in response to IFN-gamma treatment. CIITA promoter analysis confirmed that pIV is IFN-gamma inducible in B cells and that the GAS and IRF-E sites are necessary for full induction. DNA binding of IRF-1 and IRF-2, members of the IFN regulatory factor family, was up-regulated in B cells in response to IFN-gamma and increased the activity of CIITA pIV. In vivo genomic footprint analysis demonstrated proteins binding at the GAS, IRF-E and E box sites of CIITA pIV. Although CIITA pIII is considered to be the hematopoietic-specific promoter of CIITA, these findings demonstrate that pIV is active in B lymphocytes and potentially contributes to the expression of CIITA and MHC II in these cells.
MHC II类反式激活因子（CIITA）是MHC II类（MHC II）表达的主要调节因子，是一种控制MHC II转录的共激活因子。由于CIITA启动子III（pIII）（该基因四个潜在启动子（pI - pIV）之一）的持续活性，人类B淋巴细胞组成性表达MHC II。尽管已经观察到B细胞中MHC II表达因细胞因子而增加，并且在许多不同细胞类型中研究了IFN-γ对MHC II和CIITA的诱导作用，但尚未研究IFN-γ对B细胞中CIITA表达的具体影响。为了研究IFN-γ对B细胞中CIITA表达的调节作用，进行了逆转录聚合酶链反应（RT-PCR）、体内和体外蛋白质/DNA结合研究以及功能性启动子分析。IFN-γ处理后，人类B淋巴细胞中MHC II和CIITA IV型特异性RNA均增加。CIITA启动子分析证实，pIV在B细胞中可被IFN-γ诱导，并且GAS和IRF-E位点对于完全诱导是必需的。IFN调节因子家族成员IRF-1和IRF-2的DNA结合在B细胞中因IFN-γ而上调，并增加了CIITA pIV的活性。体内基因组足迹分析表明蛋白质结合在CIITA pIV的GAS、IRF-E和E盒位点。尽管CIITA pIII被认为是CIITA的造血特异性启动子，但这些发现表明pIV在B淋巴细胞中具有活性，并可能有助于这些细胞中CIITA和MHC II的表达。
