CTF5--a new transcriptional activator of the NFI/CTF family.

NFI/CTF is a family of polypeptides involved in stimulating the initiation of adenovirus DNA replication and the activation of transcription driven by RNA polymerase II. Several naturally occurring NFI/CTF variants display distinctive transactivation activities in vivo. To define more precisely the role of the NFI/CTF family in regulating gene expression, we cloned the splice variant CTF5, analyzed transcriptional activation patterns in a yeast transcription assay, and compared it with other CTF proteins. CTF5, which lacks exons 9 and 10 including a CTD-like motif essential for transcriptional activation by full-length CTF1, enhances transcription to a greater extent than CTF1. In addition, CTF5 is even more active than CTF7, which lacks exons 7-9. These findings indicate that CTF proteins formed by differential splicing display a much broader range of transcriptional activities as observed previously.