While the proper selection of splice sites is essential for genomic diversity, adaptive growth and development, errors in splicing can have enormous detrimental effects on function and are now recognized as the underlying cause for many human diseases. Indeed, splicing errors are associated with muscular dystrophy, Alzheimer's disease, parkinsonism, psychiatric disorders, ataxias and cancers making the study of factors that control splice-site selection vitally important for human disease. Splicing occurs at the spliceosome, a macromolecular complex composed of several RNAs and numerous proteins. Critical to normal gene splicing is the proper selection of the 5'and 3'splice sites, events that occur early in the development of the spliceosome and whose specificity is guided by an essential family of splicing factors known as SR proteins. The phosphorylation states of SR proteins directly impact their subcellular localization and splicing activities but our understandig of how these different forms are attained is, at best, incomplete. SR protein nuclear entry and splicing function are driven by a basal level of phosphorylation (hypo-phosphorylation) catalyzed by the SRPK family of protein kinases. However, this simple paradigm of one kinase-one substrate is now being challenged as a second protein kinase family has emerged as critical SR protein regulators. The Clk family of kinases can increase SR protein phosphoryl content to a greater extent than the SRPKs, generating hyper-phosphorylated forms that are largely uncharacterized at both structural and functional levels. While they differ substantially from the SRPKs in several ways, most importantly, Clk kinases possess an additional noncatalytic domain that we showed recently is responsible for its unique hyper-phosphorylating activity. Despite its significance in controlling SR protein function and splicing, little is known about the Clk enzymes. Using novel phosphate mapping and structural techniques combined with cell-based assays, we will investigate how the Clk kinases hyper-phosphorylate SR proteins and modulate splicing.

Public Health Relevance

Although many human diseases including neurodegenerative disorders and cancers are linked to mistakes in gene splicing, what controls the selection of splice sites in the cell is still poorly understood. To understand the link between disease and gene processing, we are studying how unique phosphorylation states in an essential group of splicing factors (SR proteins) are catalyzed by the Clk family of enzymes and regulate the selection of correct splice sites.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM098528-01A1
Application #
8294209
Study Section
Macromolecular Structure and Function B Study Section (MSFB)
Program Officer
Bender, Michael T
Project Start
2012-06-01
Project End
2016-03-31
Budget Start
2012-06-01
Budget End
2013-03-31
Support Year
1
Fiscal Year
2012
Total Cost
$294,405
Indirect Cost
$104,405
Name
University of California San Diego
Department
Pharmacology
Type
Schools of Medicine
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093
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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
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
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
Keshwani, Malik M; Hailey, Kendra L; Aubol, Brandon E et al. (2015) Nuclear protein kinase CLK1 uses a non-traditional docking mechanism to select physiological substrates. Biochem J 472:329-38
Aubol, Brandon E; Plocinik, Ryan M; Keshwani, Malik M et al. (2014) N-terminus of the protein kinase CLK1 induces SR protein hyperphosphorylation. Biochem J 462:143-52
Aubol, Brandon E; Plocinik, Ryan M; Hagopian, Jonathan C et al. (2013) Partitioning RS domain phosphorylation in an SR protein through the CLK and SRPK protein kinases. J Mol Biol 425:2894-909
Aubol, Brandon E; Jamros, Michael A; McGlone, Maria L et al. (2013) Splicing kinase SRPK1 conforms to the landscape of its SR protein substrate. Biochemistry 52:7595-605
Aubol, Brandon E; Plocinik, Ryan M; McGlone, Maria L et al. (2012) Nucleotide release sequences in the protein kinase SRPK1 accelerate substrate phosphorylation. Biochemistry 51:6584-94