Estradiol-dependent transcription initiation upstream from the chicken apoVLDLII gene coding for the very-low-density apolipoprotein II.

We have investigated RNAs originating from the 5'-flanking region of the chicken very-low-density apolipoprotein II (apoVLDLII) gene. S1 nuclease mapping and primer extension experiments revealed two minor upstream transcription start points located 1105 and 1530 nucleotides in front of the apoVLDLII gene. Transcription starting at these points is dependent upon estradiol as is transcription from the major start points. The transcripts are polyadenylated, but are not detectable in polysomes. Run-on assays indicated that the low concentration of the upstream initiated transcripts is due both to low transcription levels and to low transcript stability. The sequence around the upstream start points does not show strong homologies with consensus sequences of promoters for eukaryotic protein encoding genes. Nevertheless, the upstream sequences are transcribed in vivo by RNA polymerase II.