Adenovirus inhibition of cellular protein synthesis involves inactivation of cap-binding protein

Adenovirus (Ad) infection results in a marked inhibition of cellular protein synthesis that initiates during the late phase of the viral infectious cycle. We show that the mechanism used for suppression of cellular protein synthesis during cell cycle progression is exploited by Ad to repress host and enhance late viral mRNA translation. Discrimination between cellular and late Ad mRNAs and inhibition of host protein synthesis are shown to involve viral-mediated underphosphorylation of cap-binding protein (CBP) and subsequent inactivation of CBP complex, a large enzymatic complex required for cap-dependent mRNA translation. Late Ad mRNAs, like those of poliovirus, possess the unique ability to translate independent of a normal cap recognition process and do not require the activity of CBP complex. Inhibition of cellular translation by these two viruses is quite similar, except that whereas CBP complex is proteolytically degraded by poliovirus, it is functionally inactivated by Ad.