title: NLR family member NLRC5 is a transcriptional regulator of MHC class I genes.
abstract: MHC class I plays a critical role in the immune defense against viruses and tumors by presenting antigens to CD8 T cells. An NLR protein, class II transactivator (CIITA), is a key regulator of MHC class II gene expression that associates and cooperates with transcription factors in the MHC class II promoter. Although CIITA also transactivates MHC class I gene promoters, loss of CIITA in humans and mice results in the severe reduction of only MHC class II expression, suggesting that additional mechanisms regulate the expression of MHC class I. Here, we identify another member of the NLR protein family, NLRC5, as a transcriptional regulator of MHC class I genes. Similar to CIITA, NLRC5 is an IFN-gamma-inducible nuclear protein, and the expression of NLRC5 resulted in enhanced MHC class I expression in lymphoid as well as epithelial cell lines. Using chromatin immunoprecipitation and reporter gene assays, we show that NLRC5 associates with and activates the promoters of MHC class I genes. Furthermore, we show that the IFN-gamma-induced up-regulation of MHC class I requires NLRC5, because knockdown of NLRC5 specifically impaired the expression of MHC class I. In addition to MHC class I genes, NLRC5 also induced the expression of beta2-microglobulin, transporter associated with antigen processing, and large multifunctional protease, which are essential for MHC class I antigen presentation. Our results suggest that NLRC5 is a transcriptional regulator, orchestrating the concerted expression of critical components in the MHC class I pathway.
authors.affiliation: Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
authors.forename: Torsten B
authors.initials: TB
authors.lastname: Meissner
authors.forename: Amy
authors.initials: A
authors.lastname: Li
authors.forename: Amlan
authors.initials: A
authors.lastname: Biswas
authors.forename: Kyoung-Hee
authors.initials: KH
authors.lastname: Lee
authors.forename: Yuen-Joyce
authors.initials: YJ
authors.lastname: Liu
authors.forename: Erkan
authors.initials: E
authors.lastname: Bayir
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Iliopoulos
authors.forename: Peter J
authors.initials: PJ
authors.lastname: van den Elsen
authors.forename: Koichi S
authors.initials: KS
authors.lastname: Kobayashi
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D005786:Gene Expression Regulation; D005805:Genes, MHC Class I; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C548042:NLRC5 protein, human; D034741:RNA, Small Interfering