ENHANCED SPLICING OF NONCONSENSUS 3'-SPLICE SITES LATE DURING ADENOVIRUS INFECTION

The adenovirus major late transcription unit is an example of an alter natively spliced gene, in which a common 5' splice site can be spliced to more than 15 different 3' splice sites. Here we show that the spec ificity in 3' splice site recognition changes during virus infection, such that 3' splice sites with long consensus-type polypyrimidine trac ts are repressed while 3' splice sites with short atypical polypyrimid ine tracts, which bind U2AF(65K) inefficiently, are enhanced in splici ng in late virus-infected nuclear extracts. On the basis of these expe riments, we discuss a mechanism that helps to explain how the complex pattern of major late mRNAs is produced late during virus infection.