The polyomavirus early promoter: role of proximal promoter elements in the formation of 5' termini in vivo.

Analysis of polyomaviruses with altered early promoter sequences indicates that in vivo (1) the polyomavirus early ATA motif and nearby upstream sequences dictate homogeneity of 5' termini, in contrast to what has been observed in vitro, where the cap site was reported to affect homogeneity of 5' termini (P. Jat, V. Novak, A. Cowie, C. Tyndall, and R. Kamen, 1982, Mol. Cell. Biol. 2, 737-751). (2) Substitution of the polyomavirus ATA motif by the adenovirus 2 major later promoter suppresses minor early 5' termini between the origin and the early cap sites, indicating that these termini are not the result of DNA replication.