Analysis of a predicted nuclear localization signal: implications for the intracellular localization and function of the Saccharomyces cerevisiae RNA-binding protein Scp160.

Gene expression is controlled by RNA-binding proteins that modulate the synthesis, processing, transport and stability of various classes of RNA. Some RNA-binding proteins shuttle between the nucleus and cytoplasm and are thought to bind to RNA transcripts in the nucleus and remain bound during translocation to the cytoplasm. One RNA-binding protein that has been hypothesized to function in this manner is the Saccharomyces cerevisiae Scp160 protein.

Functional overlap between conserved and diverged KH domains in Saccharomyces cerevisiae SCP160.

The K homology (KH) domain is a remarkably versatile and highly conserved RNA-binding motif. Classical KH domains include a characteristic pattern of hydrophobic residues, a Gly-X-X-Gly (GXXG) segment, and a variable loop. KH domains typically occur in clusters, with some retaining their GXXG sequence (conserved), while others do not (diverged).

Both KH and non-KH domain sequences are required for polyribosome association of Scp160p in yeast.

Scp160p is a 160 kDa RNA-binding protein in yeast previously demonstrated to associate with specific messages as an mRNP component of both soluble and membrane-bound polyribosomes. Although the vast majority of Scp160p sequence consists of 14 closely spaced KH domains, comparative sequence analyses also demonstrate the presence of a potential nuclear localization sequence located between KH domains 3 and 4, as well as a 110 amino acid non-KH N-terminal region that includes a potential nuclear export sequence (NES). As a step toward investigating the structure/function relationships of Scp160p, we generated two truncated alleles, FLAG.