Identification of a high-molecular-weight cellular protein complex containing the adenovirus DNA binding protein

The adenovirus DNA binding protein (DBP) functions in a number of diverse processes that include viral DNA replication and host range determination. A subpopulation of DBP has been found to exist in a high-molecular-weight (HMWDBP) complex of greater than 650 kDa. This complex was stable to high salt and low levels of detergent in the presence of DTT at 4 degrees. While the complex prepared in high salt was devoid of nucleic acid, it retained its ability to bind to ssDNA. Electron microscopic (EM) analysis in the presence of M13 ssDNA verified its interaction with ssDNA. The complex exists as particles approximately 25-30 nm based on EM analysis of negatively stained samples in the absence of DNA. No viral replication components were detected in the HMWDBP complex, suggesting that it is not a viral replication complex. The HMWDBP complex prepared under a variety of infection conditions contained a consistent set of proteins. HMWDBP complex was also detected in the absence of viral infection in gmDBP6 cells (a HeLa cell derivative that expresses DBP from the dexamethasone-inducible MMTV promoter). These results suggest that the components of the complex, other than DBP, are host encoded.