EVI-1 ZF1 DNA-BINDING ACTIVITY AND A 2ND DISTINCT TRANSCRIPTIONAL REPRESSOR REGION ARE BOTH REQUIRED FOR OPTIMAL TRANSFORMATION OF RAT1 FIBROBLASTS

The Evi-1 gene encodes a zinc finger transcriptional repressor protein that normally plays a role in development and is frequently activated in myeloid leukaemias, Evi-1 has two distinct DNA binding domains, ZF 1 and ZF2, and a defined repressor domain but the function of the rema inder of the molecule is unknown. The ZF2 and repressor domains have b een shown to be required for transformation and we show here that ZF1 is also required. An alternative splice variant of Evi-1, designated D elta 324, encodes a protein which lacks a portion of the ZF1 DNA bindi ng domain and the intervening amino acids 239-514 (designated IR) loca ted between ZF1 and the repressor domain, We show that Delta 324 can n either bind ZF1, repress transcription through this site nor transform Rat1 fibroblasts, Reconstitution studies demonstrate that the defect in Delta 324 is partially complemented by recreating the ZF1 DNA bindi ng activity. However, full function also requires the IR region which has transcriptional repressor activity. This study shows therefore, th at ZF1, ZF2 and repressor domains and the IR region all contribute to the transformation efficiency of the Evi-1 protein.