Identification of Epstein-Barr virus nuclear antigen 1 protein domains that direct interactions at a distance between DNA-bound proteins.

The EBNA1 protein of Epstein-Barr virus (EBV) binds to and activates DNA replication from the EBV latent origin of replication, oriP, via a direct interaction with the two noncontiguous subelements of oriP. The EBNA1 molecules bound to the oriP subelements interact efficiently with each other by a DNA looping mechanism. We have previously mapped a region of EBNA1 (termed the looping region) that is required to mediate the interaction of the EBNA1 molecules bound to the oriP subelements. We now demonstrate that two fragments of this region of EBNA1, which consist largely of an eight amino acid repeat, can mediate homotypic interactions when transferred to another DNA-binding protein. Protein interactions mediated by the EBNA1 looping region appear to be dependent on DNA binding since these interactions were detected between DNA-bound forms of the proteins only.