SR protein

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An overview of SR proteins and their role in RNA splicing

SR proteins are a family of RNA-binding proteins that play a crucial role in the splicing of pre-mRNA in eukaryotic cells. These proteins are characterized by the presence of one or two RNA recognition motifs (RRMs) at their N-terminus and a C-terminal domain rich in serine and arginine residues, known as the RS domain. The RS domain is essential for protein-protein interactions and for the recruitment of the splicing machinery.

Structure

SR proteins are defined by their modular structure, which typically includes:

• One or two RNA recognition motifs (RRMs) that bind to specific RNA sequences.
• A C-terminal RS domain that is rich in serine and arginine residues. This domain is involved in protein-protein interactions and is often phosphorylated, which regulates the activity of the SR proteins.

Function

SR proteins are primarily involved in the regulation of alternative splicing, a process that allows a single gene to produce multiple protein isoforms. They function by binding to exonic splicing enhancers (ESEs) and recruiting the spliceosome to the correct splice sites. This recruitment is crucial for the accurate removal of introns and the joining of exons in the pre-mRNA.

Role in Alternative Splicing

Alternative splicing is a mechanism that increases the diversity of proteins that can be produced by a single gene. SR proteins influence this process by:

• Binding to ESEs and promoting the inclusion of specific exons.
• Interacting with other splicing factors to modulate splice site selection.
• Being involved in the regulation of splicing in response to cellular signals and conditions.

Phosphorylation

The activity of SR proteins is regulated by phosphorylation. The RS domain is a target for several kinases, including the SR protein kinases (SRPKs) and Clk/Sty kinases. Phosphorylation affects the localization, activity, and interactions of SR proteins, thereby influencing splicing outcomes.

Clinical Significance

Dysregulation of SR proteins has been implicated in various diseases, including cancer and neurodegenerative disorders. Mutations or altered expression of SR proteins can lead to aberrant splicing patterns, contributing to disease pathogenesis.

Research and Applications

SR proteins are a focus of research due to their central role in splicing and their potential as therapeutic targets. Modulating the activity of SR proteins or their phosphorylation status could provide new avenues for the treatment of diseases associated with splicing defects.

Also see

• RNA splicing
• Alternative splicing
• Spliceosome
• RNA-binding protein
• Exonic splicing enhancer