NLRC5: a newly discovered MHC class I transactivator (CITA)

Major histocompatibility complex (MHC) class I and class II are crucial for the function of the human adaptive immune system. An NLR protein, CIITA (MHC class II transactivator), is a master regulator of MHC class 11 gene expression as well as of some of the genes involved in MHC class II antigen presentation. It has recently been discovered that another member of the NI:.,R protein family, NLRC5, transcriptionally activates MHC class I genes, and thus acts as CITA (MHC class I transactivator), a counterpart to CIITA. In addition to MHC class I genes, NLRC5 can induce the expression of beta 2M, TAP1 and LMP2, essential components of MHC class I antigen presentation. These findings indicate that NLRC5 and CIITA are transcriptional regulators that orchestrate the concerted expression of critical components in the MHC class I and MHC class 11 pathways, respectively. (C) 2011 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.