A rational nomenclature for serine/arginine-rich protein splicing factors (SR proteins)

The serine/arginine-rich proteins (SR proteins) constitute a family of predominantly nuclear RNA-binding proteins that are present in all metazoan organisms and in plants. The first SR protein was identified nearly 20 years ago as an essential pre-mRNA splicing factor that could also influence alternative splicing in human cell extracts, and was found to have sequence features similar to genetically defined splicing regulators in Drosophila (Ge et al. 1991; Krainer et al. 1991). Specifically, it contained two N-terminal RNP-type RNA-binding domains (RBDs; also known as an RNA recognition motif [RRM]), and a C-terminal region enriched in Arg–Ser dipeptides (RS domain). It was soon realized that a family of SR proteins exists in mammals that are characterized by one or two N-terminal RBDs and a C-terminal RS domain (Fu and Maniatis 1992; Zahler et al. 1992). The SR proteins have since been extensively studied in several species, and found to play important roles in splicing, both as general splicing factors and as regulators of alternative splicing. Unexpectedly, studies during the past decade have extended the role of SR proteins to a diverse set of additional cellular processes, including mRNA nuclear export, mRNA stability and quality control, translation, maintenance of genomic stability, oncogenic transformation, and likely others (Huang and Steitz 2005; Long and Cáceres 2009; Zhong et al. 2009). It is thus apparent that SR proteins play multiple important roles in the control of gene expression