ERM, A PEA3 SUBFAMILY OF ETS TRANSCRIPTION FACTORS, CAN COOPERATE WITH C-JUN

A human cDNA clone for ERM, a member of the ets gene family, has been obtained by polymerase chain reaction with degenerate primers corresponding to highly conserved regions within an Ets DNA binding domain. ERM mRNA is expressed ubiquitously. The gene was mapped to chromosome 3q27. In in vivo transient-expression assays, ERM induced transcription more efficiently from a synthetic element containing both an ets-binding site (EBS) and a cyclic AMP response element (CRE) than from one containing an EBS alone. The activation of a synthetic EBS-CRE site by ERM was likely to involve a leucine zipper protein capable of dimerizing with CRE-BP1 leucine zipper. Indeed, ERM and c-Jun synergistically activated the EBS-CRE without making an apparent ternary complex. The synergy between c-Jun and ERM may be attributed to the enhancing effect of c-Jun on the transcription activity of ERM, because c Jun increased ERM transcription activity by more than 20-fold in an assay system using a variety of fusion proteins between a Ga14 DNA-binding domain and a portion of ERM. This enhancing effect of c-Jun required the amino-terminal portion of ERM.