REPLICATION PROTEIN-A IS A COMPONENT OF A COMPLEX THAT BINDS THE HUMAN METALLOTHIONEIN-IIA GENE-TRANSCRIPTION START SITE

Previous studies revealed that sequences surrounding the initiation si tes in many mammalian and viral gene promoters, called initiator (Inr) elements, may be essential for promoter strength and for determining the actual transcription start sites. DNA sequences in the vicinity of the human metallothionein IIA (hMTIIA) gene transcription start site share homology with some of the previously identified Inr elements. Ho wever, in the present study we have found by in vitro transcription as says that the hMTIIA promoter does not contain a typical Inr. Electrop horetic mobility shift assays identified several DNA-protein complexes at the hMTIIA gene transcription start site. A partially purified pro tein fraction containing replication protein A (RPA) binds to the hMTI IA gene transcription start site and represses transcription from the hMTIIA promoter in vitro. In addition, overexpression of the human 70- kDa RPA-1 protein represses transcription of a reporter gene controlle d by the hMTIIA promoter in vivo. These findings suggest that hMTIIA t ranscription initiation is controlled by a mechanism different from mo st mammalian and viral promoters and that the previously identified RP A may also be involved in transcription regulation.