Evaluating the role of CRM1-mediated export for adenovirus gene expression

Abstract

A complex of the Adenovirus (Ad) early region 1b 55-kDa (E1b-55kDa) and early region 4 ORF6 34-kDa (E4-34kDa) proteins promotes viral late gene expression. E1b-55kDa and E4-34kDa have leucine-rich nuclear export signals (NESs) similar to that of HIV Rev. It was proposed that E1b-55kDa and/or E4-34kDa might promote the export of Ad late mRNA via their Rev-like NESs, and the transport receptor CRM1. We treated infected cells with the cytotoxin leptomycin B to inhibit CRM1-mediated export; treatment initially delays the onset of late gene expression, but this activity completely recovers as the late phase progresses. We find that the E1b-55kDa NES is not required to promote late gene expression. Previous results showed that E4-34kDa-mediated late gene expression does not require an intact NES (J. Virol. 74 (2000), 6684–6688). Our results indicate that these Ad regulatory proteins promote late gene expression without intact NESs or active CRM1.