UHMK1 is a novel splicing regulatory kinase

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• U2AF Homology Motif Kinase 1 (UHMK1) possesses a unique U2AF homology motif, interacting with splicing factors SF1 and SF3B1.
• While UHMK1 phosphorylates splicing factors in vitro, its direct role in RNA processing and gene expression remained unelucidated.
• Understanding UHMK1's function is crucial for comprehending spliceosome assembly and gene regulation.

Purpose of the Study:

• To identify novel UHMK1 substrates and elucidate its role in RNA processing and gene expression.
• To investigate the impact of UHMK1 modulation on cellular processes including splicing, proliferation, and migration.
• To integrate phosphoproteomics, RNA-seq, and bioinformatics to comprehensively analyze UHMK1's function.

Main Methods:

• Global phosphoproteomics and RNA-sequencing (RNA-seq) were employed to identify differentially phosphorylated proteins and gene expression changes.
• Bioinformatic approaches, including Gene Ontology analysis, were used to interpret the functional significance of identified substrates.
• Splicing reporter assays and functional assays (proliferation, migration, colony formation) were performed to validate UHMK1's role.

Main Results:

• UHMK1 modulation led to differential phosphorylation of 117 proteins, with 106 novel putative substrates identified.
• UHMK1 significantly impacted over 270 alternative splicing events and showed enrichment in splicing-related Gene Ontology terms.
• UHMK1 knockdown had a minor effect on transcript expression but influenced epithelial-mesenchymal transition, proliferation, and migration.

Conclusions:

• UHMK1 functions as a splicing regulatory kinase, linking protein phosphorylation to gene expression.
• The study identifies novel UHMK1 substrates and demonstrates its involvement in key cellular processes like splicing and cell migration.
• These findings establish UHMK1 as a critical regulator in mRNA processing and cellular function.