Possible involvement of the mouse Grg protein in transcription.

The mouse Grg gene encodes a 197 amino acid nuclear protein homologous to the amino-terminal domain of the product of the groucho (gro) gene of the Drosophila Enhancer of split complex. Recent work has suggested that the gro protein functions as a transcriptional corepressor during Drosophila development. We therefore examined possible roles of the mouse Grg protein in DNA binding and in vitro transcription. No sequence-specific DNA binding activity was detected by polymerase chain reaction-DNA binding site selection nor was the glutamine-rich Grg protein capable of acting as an activation domain in an in vivo transactivation assay. However, depletion of Grg protein from HeLa nuclear extracts inhibited the in vitro transcription activity of the extracts. We suggest that Grg protein may interact with components of the basal transcription machinery.