Binding modes of the precursor of adenovirus major core protein VII to DNA and template activating factor I: implication for the mechanism of remodeling of the adenovirus chromatin.

Template Activating Factor (TAF) I remodels the adenovirus (Ad) core structure composed of the Ad genome DNA and basic viral core proteins and stimulates in vitro DNA replication and transcription of the Ad core. We have recently reported that TAF-I binds to major core protein VII and forms DNA-protein VII-TAF-I ternary complexes in vitro and in vivo. Further to understand the mechanism of remodeling of the Ad core, we characterized the interaction mode between the precursor of protein VII (pre-VII) and either DNA or TAF-I by means of biochemical and biophysicochemical methods. We found that a major binding region of pre-VII with both DNA and the acidic carboxyl-terminal region of TAF-I lies in the arginine-rich region of pre-VII. Both amino-terminal and carboxyl-terminal regions of pre-VII without the arginine-rich region directly bound to DNA and supported the DNA binding activity of the arginine-rich region. A TAF-I mutant protein lacking the acidic carboxyl-terminal region bound preferentially to the carboxyl-terminal region of pre-VII containing the arginine-rich region rather than the amino-terminal region of pre-VII. Thus, DNA interacted with the entire region of pre-VII, while TAF-I bound preferentially to the carboxyl-terminal region of pre-VII. This binding mode suggests the formation of the ternary complexes among DNA, protein VII, and TAF-I. On the basis of the binding modes in binary systems, we discussed the remodeling mechanism of the Ad core in early phases of infection.