Regulation of the human transforming growth factor beta type II receptor gene promoter by novel Sp1 sites

The transforming growth factor-beta (TGF beta) type II receptor (T betaR-II ) is responsible for transducing the growth inhibitory signals of TGF beta. The T betaR-II gene promoter lacks both a TATA box and a CAAT box near the transcription initiation site, and has been shown to contain binding seque nces for several transcription factors (Sp1, AP1, NF-Y, Cut and ERT) which are important for T betaR-II gene promoter activity in vitro. However, it i s still not clear which interactions are important for the regulation of T betaR-II gene promoter activity in vivo. Using in viro genomic DNA footprin ting of normal human epithelial cells (HaCaT), we have identified two novel identical and strongly protected sites (ggggctgg) at positions -59 and - 1 02 of the T betaR-II gene promoter. Mutation of either site significantly r educed promoter activity in transient transfections. Protein binding to the se sites, as determined by electrophoretic mobility shift assays (EMSA), wa s specifically competed with consensus Sp1 oligonucleotides. Furthermore, a nti-Sp1/3 antibodies produced band shifts when incubated with the T betaR-I I - 59 and - 102 DNA probes. Importantly, Sp1 protein binding was influence d by the presence of an intact NF-Y binding site at position -83. Our data suggests that both Sp1 and NF-Y may play an important role in regulating T betaR-II gene promoter basal activity in vivo.