Accurate in vitro transcriptional initiation of the chick alpha 2 (Type I) collagen gene

Chick genomic DNA containing the extreme 5' end of the alpha 2 (type I) collagen gene has been used as template in an in vitro HeLa cell transcription system. RNA polymerase II-dependent transcription initiates from a specific site on this DNA. The precise location of this site was determined by three types of experiments: sizing of in vitro-synthesized RNA runoff transcripts, comparing the sequence of the in vitro-made RNA transcripts with the structure of the DNA template, and identifying the first and second nucleotides of the in vitro-synthesized transcripts. Transcription was found to initiate 33 base pairs downstream from a canonical Goldberg-Hogness sequence (TATAAATA). This in vitro start site is the same as the initiation site of in vivo-synthesized collagen RNA.