CIITA

CIITA is a human is_associated_with::gene which encodes a is_associated_with::protein called the class II, major histocompatibility complex, transactivator. Mutations in this gene are responsible for the is_associated_with::bare lymphocyte syndrome in which the is_associated_with::immune system is severely compromised and cannot effectively fight is_associated_with::infection. Chromosomal rearrangement of CIITA is involved in the pathogenesis of is_associated_with::Hodgkin lymphoma and is_associated_with::primary mediastinal B cell lymphoma.

Function
CIITA mRNA can only be detected in is_associated_with::human leukocyte antigen (HLA) system class II-positive cell lines and tissues. This highly restricted tissue distribution suggests that expression of HLA class II genes is to a large extent under the control of CIITA. However CIITA does not appear to directly bind to DNA. Instead CIITA functions through activation of the is_associated_with::transcription factor is_associated_with::RFX5. Hence CIITA is classified as a transcriptional coactivator.

The CIITA protein contains an acidic transcriptional activation domain, 4 LRRs (is_associated_with::leucine-rich repeats) and a GTP binding domain. The protein uses GTP binding to facilitate its own transport into the nucleus. Once in the nucleus, the protein acts as a positive regulator of class II major histocompatibility complex is_associated_with::gene transcription, and is often referred to as the "master control factor" for the expression of these genes.

Interactions
CIITA has been shown to interact with is_associated_with::RFX5, is_associated_with::MAPK1, is_associated_with::XPO1, is_associated_with::Nuclear receptor coactivator 1, is_associated_with::RFXANK and is_associated_with::ZXDC.