TRANSCRIPTIONAL REPRESSION BY THE HUMAN HOMEOBOX PROTEIN EVX1 IN TRANSFECTED MAMMALIAN-CELLS

The human homeobox protein EVX1 (EVX1) is thought to play an important role during embryogenesis. In this study, the effect of EVX1 on gene transcription has been investigated in transfected mammalian cells. EV X1 expression represses transcription of a reporter gene directed by e ither cell-specific or viral promoter/enhancer sequences in a variety of mammalian cell lines and in a concentration-dependent manner. Trans criptional repression is independent of the presence of DNA-binding si tes for EVX1 in all the promoters we tested. Furthermore, repression b y EVX1 is evident also using a TATA-less minimal promoter in the repor ter construct. A carboxyl-terminal proline/alanine-rich region of EVX1 seems to be responsible for the transcriptional repression activity, as suggested by transfection of EVX1 mutants. We speculate that the re pressor function of EVX1 contributes to its proposed role in embryogen esis.