Major histocompatibility complex (MHC) class I and class II molecules play critical roles in the activation of the adaptive immune system by presenting antigens to CD8+ and CD4+ T cells, respectively. Although it has been well known that CIITA (MHC class II transactivator), an NLR (nucleotide-binding domain, leucine-rich-repeat containing) protein, as a master regulator of MHC class II gene expression, the mechanism of MHC class I gene transactivation was unclear. Recently, another NLR protein, NLRC5 (NLR family, CARD domain-containing 5), was identified as an MHC class I transactivator (CITA). NLRC5 is a critical regulator for the transcriptional activation of MHC class I genes and other genes involved in the MHC class I antigen presentation pathway. CITA/NLRC5 plays a crucial role in human cancer immunity through the recruitment and activation of tumor killing CD8+ T cells. Here, we discuss the molecular function and mechanism of CITA/NLRC5 in the MHC class I pathway and its role in cancer.

中文翻译：

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I类反式激活因子NLRC5：MHC I类途径和癌症免疫监测的核心参与者。

主要的组织相容性复合体（MHC）I类和II类分子通过分别向CD8 +和CD4 + T细胞呈递抗原，在适应性免疫系统的激活中发挥关键作用。虽然众所周知，CIITA（MHC II类反式激活因子）是一种NLR（核苷酸结合域，富含亮氨酸的重复序列）蛋白，作为MHC II类基因表达的主要调控因子，但它是MHC I类基因的机制反式激活尚不清楚。最近，另一种NLR蛋白NLRC5（NLR家族，含有5个CARD结构域）被鉴定为MHC I类反式激活因子（CITA）。NLRC5是MHC I类基因和参与MHC I类抗原呈递途径的其他基因转录激活的关键调控因子。CITA / NLRC5通过募集和激活杀死肿瘤的CD8 + T细胞，在人类癌症免疫中起着至关重要的作用。在这里，我们讨论CITA / NLRC5在MHC I类途径中的分子功能和机制及其在癌症中的作用。