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Epstein–Barr virus nuclear antigen 1
Epstein–Barr nuclear antigen 1 (EBNA1) is a multifunctional, dimeric viral protein associated with Epstein–Barr virus (EBV).〔 It is the only EBV protein found in all EBV-related malignancies.〔〔 It is important in establishing and maintaining the altered state that cells take when infected with EBV. EBNA1 has a glycine–alanine repeat sequence that separates the protein into amino- and carboxy-terminal domains. This sequence also seems to stabilize the protein, preventing proteasomal breakdown, as well as impairing antigen processing and MHC class I-restricted antigen presentation. This thereby inhibits the CD8-restricted cytotoxic T cell response against virus-infected cells. The EBNA1 transcript area originates at the Qp promoter during latency phases I and II.〔 It is the only viral protein expressed during the first latency phase.〔〔
==Function==
EBNA1 is integral in many EBV functions including gene regulation, extrachromosomal replication, and maintenance of the EBV episomal genome through positive and negative regulation of viral promoters.〔〔 Studies show that the phosphorylation of ten specific sites on EBNA1 regulates these functions. When phosphorylation does not occur, replication and transcription activities of the protein are significantly decreased.〔 EBNA1 acts through sequence-specific binding to the plasmid origin of viral replication (oriP) within the viral episome. The oriP has four EBNA1 binding sites where replication is initiated as well as a 20-site repeat segment which also enhances the presence of the protein.〔 EBNA1’s specific binding ability, as well as its ability to tether EBV DNA to chromosomal DNA, allows EBNA1 to mediate replication and partitioning of the episome during division of the host cell.〔〔 EBNA1 also interacts with some viral promoters via several mechanisms, further contributing to transcriptional regulation of EBNA1 itself as well as the other EBNAs (2 and 3) and of EBV latent membrane protein 1 (LMP1).〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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