Resolving the functions of overlapping viral genes by site-specific mutagenesis at a mRNA splice site

Abstract
Early region IA of human adenoviruses encodes a function required for normal induction of early viral genes and virus-induced cell transformation. The region is expressed at early times as 2 overlapping spliced mRNA, 12S and 13S, which encode closely related proteins. To distinguish between the functions of these proteins, a single T .fwdarw. G transversion was constructed which prevents splicing of the 12S mRNA. This transversion, in the 2nd base of the 12S mRNA intron, does not alter the protein encoded by the 13S mRNA due to degeneracy in the genetic dose. Only the 13S mRNA appears to encode the regulatory protein required for normal early gene expression.