Characterization of two novel YY1 binding sites in the polyomavirus late promoter

NF-D is a ubiquitous nuclear factor that has been shown to bind specifically to a DNA element in the polyomavirus regulatory region. In this report, we demonstrate that NF-D is either identical or very similar to a transcription factor that has been variously named YY1, delta, NF-E1, UCRBP, or CF1. Moreover, we show the presence in the polyomavirus genome of a second DNA motif, located 40 bp from the first, which binds YY1/NF-D with high affinity. Both sites lie downstream of the major late transcription initiation sites. By site directed mutagenesis,,ve demonstrate that both elements contribute positively to the activity of the late promoter, probably by a cooperative mechanism. We also demonstrate that the requirement of the YY1/NF-D function for late promoter activity varies with the cell line.