EBNA, or Epstein-Barr nuclear antigens, are proteins expressed in the Epstein-Barr virus (EBV), which causes infectious mononucleosis. EBNA-1 has a length of 641 residues and a predicted mass of 56.4 kDa. This dimerizing protein has crucial roles in maintaining the viral DNA during latent infection, as well as in gene regulation. It is also consistently expressed in EBV-related malignancies. EBNA-2, with a reported 487 residues and mass of 52.5 kDa, plays a role in host B-cell proliferation. EBNA-3 is also believed to play a role in B-cell immortailzation.