The adeno-associated virus Rep78 major regulatory protein forms multimeric complexes and the domain for this activity is contained within the carboxy-half of the molecule.

The adeno-associated virus (AAV) encoded Rep78 is a multifunctional protein which is able to regulate transcription, is required for AAV DNA replication, and appears necessary for site specific integration of AAV DNA into human chromosome 19. Being analogous to the large T antigen, the replication protein of polyomaviruses which is known to homo-multimerize, it seemed likely that the Rep78 protein would also interact with itself to carry out at least some of its functions. Furthermore, in electrophoretic mobility shift assay studies by many laboratories on Rep78/68 protein interaction with AAV terminal repeat DNA it has been noticed that multiple high bands often result. These data suggest Rep78-Rep78 interaction. In this study it is directly demonstrated that Rep78 is able to form multimeric complexes as measured by West-Western and chemical cross-linking assays. Furthermore, using an amino-truncated Rep78 protein, it is demonstrated that the Rep78 homo-multimerization domain is contained within the carboxy-half of the protein.