Epstein–Barr virus nuclear antigen 1

Epstein–Barr nuclear antigen 1 (EBNA1) is a multifunctional, dimeric viral protein associated with the Epstein–Barr virus (EBV). EBNA1 is the only EBV protein consistently found in all EBV-related malignancies. It plays a critical role in establishing and maintaining the altered state of cells infected with EBV.

Structure and Function

EBNA1 contains a unique glycine–alanine repeat sequence that divides the protein into distinct amino-terminal and carboxy-terminal domains. This sequence provides stability to the protein by:

• Preventing proteasomal degradation.
• Impairing antigen processing.
• Inhibiting MHC class I-restricted antigen presentation.

Through these mechanisms, EBNA1 suppresses the CD8+ T cell-mediated cytotoxic T cell response against virus-infected cells.

Expression

EBNA1 is expressed from the Qp promoter and is the only viral protein expressed during all EBV latency programs. Its consistent expression in latency highlights its importance in the persistence and survival of EBV-infected cells.

Clinical Significance

EBNA1 is crucial in EBV-related malignancies, including:

• Nasopharyngeal carcinoma
• Burkitt's lymphoma
• Hodgkin's lymphoma
• Post-transplant lymphoproliferative disorder

The ability of EBNA1 to evade immune surveillance makes it a key target for understanding EBV latency and related malignancies.