RNA-binding proteins as developmental regulators.

Abstract

Many RNA-binding proteins of the nucleus and cytoplasm, including pre-mRNA-, mRNA-, snRNA-, and pre-rRNA-binding proteins, contain a putative RNAbinding domain of approximately 90 amino acids whose amino acid sequence is conserved from yeast to man. The most highly conserved motif within this RNAbinding domain is an octapeptide, termed the ribonucleoprotein consensus sequence {RNP-CSI, which is an identifying feature of this group of proteins. Frequently, these proteins contain several similar, but nonidentical, RNP-CS-type RNA-binding domains. All of these proteins also contain at least one auxiliary domain that is unique to each type of protein and most likely functions in protein-protein interactions. Many, if not all, of the RNP-CS-type proteins display binding preferences for specific RNA sequences, and several have been shown to interact with pre-mRNA sequences important for premRNA processing. Recent work has shown that the proteins encoded by several developmental loci in Drosophila and maize contain RNP-CS and, therefore, are most likely RNA-binding proteins. Here we provide an overview of the structural characteristics of these proteins and speculate on how the modular structure of RNP-CS-type RNA-binding proteins may facilitate their participation in pathways that regulate development at the post-transcriptional level.