Krp1, a novel kelch related protein that is involved in pseudopod elongation in transformed cells

We have previously shown that the transcription factor AP-1 regulates the e xpression of genes which allow neoplastically transformed rat fibroblasts t o become invasive. Searches for further AP-1 target genes led to the identi fication of a gene encoding a novel rat kelch family member, named kelch re lated protein 1 (Krp1), Reich family members are characterized by a series of repeats at their carboxyl terminus and a BTB/POZ domain near their amino terminus. Rat Krp1 has a primarily cytoplasmic localization, and a small f raction appears to accumulate and co-localize with F-actin at membrane ruff le-like structures in the tips of pseudopodia. Overexpression of Krp1 in tr ansformed rat fibroblasts led to the formation of dramatically elongated ps eudopodia, while expression of truncated Krp1 polypeptides resulted in a re duction in the length of pseudopodia. We propose that the transformation-sp ecific expression of Krp1 is required for pseudopod elongation, which are s tructures that are required for cell motility and invasion.