Splicing is a co-transcriptional process whereby a single gene can be converted into multiple unique mRNA fragments for enhanced protein diversity. While splicing is integral for normal cellular function in complex organisms, mistakes i splice-selection can be extremely deleterious. In fact, splicing errors are associated with numerous human diseases including muscular dystrophy, Alzheimer's disease, parkinsonism, metabolic disorders, ataxias and cancers. Splicing occurs at the spliceosome, a macromolecular complex that includes both RNA and proteins. In the latter group, SR proteins are essential splicing factors that control where and how the spliceosome assembles on precursor mRNA. SR proteins contain C-terminal domains rich in arginine-serine repeats whose polyphosphorylation controls splice-site selection. The SRPK family of protein kinases phosphorylates these RS domains directing SR proteins into the nucleus for splicing activity. While SRPKs are normally localized to the cytoplasm for this function, they can enter the nucleus under certain conditions further affecting SR protein phosphorylation levels and alternative gene splicing. Although phosphorylation is critical for splice-site choice, very little is known about how residue-specific phosphorylation of SR proteins controls alternative gene splicing. Clearly, knowing how the SRPKs are regulated in the cell and how they recognize and phosphorylate SR proteins is essential for an understanding of gene splicing and disease pathologies related to mis-splicing. We showed that SRPKs and phosphatases work in opposite directions concentrating phosphates toward the C-terminal end of RS domains. We will now explore how this unique phosphate distribution termed """"""""phosphate biasing"""""""" affects SR protein function. We recently showed that the catalytic activity of SRPK1 is dependent on a nucleotide release factor composed of sequence elements from a large insert domain and an N-terminal extension. We propose that this conserved release factor is a hub for SRPK regulation in the cell. We will demonstrate how phosphorylation and protein-protein interactions modulate this factor and regulate SR protein phosphorylation levels and gene splicing.

Public Health Relevance

Incorrect splicing of genetic material is responsible for many neurodegenerative diseases and cancer. To better understand the connection between human disease and gene processing, we are studying the role of SRPKs, a critical enzyme family that regulates splicing activity in the cell.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Macromolecular Structure and Function B Study Section (MSFB)
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Bender, Michael T
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University of California San Diego
Schools of Medicine
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Aubol, Brandon E; Serrano, Pedro; Fattet, Laurent et al. (2018) Molecular interactions connecting the function of the serine-arginine-rich protein SRSF1 to protein phosphatase 1. J Biol Chem 293:16751-16760
Aubol, Brandon E; Keshwani, Malik M; Fattet, Laurent et al. (2018) Mobilization of a splicing factor through a nuclear kinase-kinase complex. Biochem J 475:677-690
Aubol, Brandon E; Hailey, Kendra L; Fattet, Laurent et al. (2017) Redirecting SR Protein Nuclear Trafficking through an Allosteric Platform. J Mol Biol 429:2178-2191
Aubol, Brandon E; Wu, Guowei; Keshwani, Malik M et al. (2016) Release of SR Proteins from CLK1 by SRPK1: A Symbiotic Kinase System for Phosphorylation Control of Pre-mRNA Splicing. Mol Cell 63:218-228
Serrano, Pedro; Aubol, Brandon E; Keshwani, Malik M et al. (2016) Directional Phosphorylation and Nuclear Transport of the Splicing Factor SRSF1 Is Regulated by an RNA Recognition Motif. J Mol Biol 428:2430-2445
Keshwani, Malik M; Aubol, Brandon E; Fattet, Laurent et al. (2015) Conserved proline-directed phosphorylation regulates SR protein conformation and splicing function. Biochem J 466:311-22
Jamros, Michael A; Aubol, Brandon E; Keshwani, Malik M et al. (2015) Intra-domain Cross-talk Regulates Serine-arginine Protein Kinase 1-dependent Phosphorylation and Splicing Function of Transformer 2?1. J Biol Chem 290:17269-81
Barkho, Sulyman; Pierce, Levi C T; Li, Sheng et al. (2015) Theoretical Insights Reveal Novel Motions in Csk's SH3 Domain That Control Kinase Activation. PLoS One 10:e0127724
Aubol, Brandon E; Adams, Joseph A (2014) Recruiting a silent partner for activation of the protein kinase SRPK1. Biochemistry 53:4625-34
Sumida, Kyohei; Kawana, Makiko; Kouno, Emi et al. (2013) Importance of UDP-glucuronosyltransferase 1A1 expression in skin and its induction by UVB in neonatal hyperbilirubinemia. Mol Pharmacol 84:679-86

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