Scp160p, an RNA-binding, polysome-associated protein, localizes to the endoplasmic reticulum of Saccharomyces cerevisiae in a microtubule-dependent manner

Scp160p is an RNA-binding protein containing 14 tandemly repeated heterogen ous nuclear ribonucleoprotein K-homology domains, which are implicated in R NA binding. Scp160p interacts with free and membrane-bound polysomes that a re dependent upon the presence of mRNA. Despite its presence on cytosolic p olysomes, Scp160p is predominantly localized to the endoplasmic reticulum ( ER). Accumulation of Scp160p-ribosome complexes at the ER requires the func tion of microtubules but is independent of the actin cytoskeleton. We propo se that the multi-K-homology-domain protein Scp160p functions as an RNA bin ding platform, interacting with polysomes that are transported to the ER.