A Study on the Functions of the E1B Minor Products of Adenovirus Type 5

Abstract

The E1b transforming region of Adenovirus type 5 encodes minor products of 93R and 156R in addition to the more abundant proteins 178R, 496R, and 84R. The goal of this study was to elucidate the function of 93R and 156R to gain a better understanding of their role in oncogenic transformation and productive infection. Mutant viruses were constructed, whose normal splicing pattern was disrupted by point mutations in the 3' acceptor sites for the 1.26 and 1.31Kb mRNAs, which code for the 156R and 93R products, respectively. In the construction of these mutations, it was necessary to ensure that they did not affect the coding region for 496R. These mutants produced transformed foci in primary rat kidney cells with wild type efficiencies in DNA-mediated transformation assays. In the mutant designed to eliminate 156R, although the two wild type 156R species were absent, two new species running slightly faster on SDS-PAGE were detected. These proteins were recognized by sera specific to both the N- and C-termini of 496R, suggesting there utilization of an in-frame cryptic splice acceptor site. Use of this site probably resulted in the production of a mRNA encoding a modified 156R. These mutant proteins also seemed to be produced at the expense of 496R. The mutant designed to eliminate 93R grew with titres equivalent to wild type dl309, yet it was not clear whether a modified protein was produced in this case as well.