Triple helix formation with the promoter of human α1(I) procollagen gene by an antiparallel triplex-forming oligodeoxyribonucleotide

The promoters of alpha 1(I) procollagen genes of vertebrates contain two contiguous stretches of polypyrimidine/polypurine sequences, referred to as C1 (-140 to -170) and C2 (-171 to -200). Antiparallel tripler-forming upstream oligonucleotides form efficient triplexes with C1. The C1 tract of human differs from rodent alpha 1(I) promoters by 7 nt which are mainly A-->G transitions. Human tripler-forming oligodeoxyribonucleotide (TFO) formed stable triplexes efficiently with a K-d of similar to 10-20 nM compared with a K-d Of similar to 100 nM for rodent TFO. Mutational analysis indicated that 3 or 4 nt (-153 to -155) are sufficient for this higher affinity. TFOs specific for human C1 inhibited transcription from human promoter both in vitro in Hela cell nuclear extracts and in vivo in cultured chick embryo fibroblasts.