PSKH1, a novel splice factor compartment-associated serine kinase

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Splicing factors, including small nuclear ribonucleoprotein particles (snRNPs) and serine/arginine-rich (SR) proteins, concentrate in nuclear splicing factor compartments (SFCs).
• SFCs are thought to store splicing factors for active gene transcription, but their dynamics and regulatory mechanisms are unclear.

Purpose of the Study:

• To investigate the localization and function of the kinase PSKH1 within nuclear SFCs.
• To elucidate the relationship between PSKH1 and SR proteins in nuclear organization and pre-mRNA splicing.

Main Methods:

• Immunofluorescence microscopy to track PSKH1 localization.
• Co-expression experiments with SR proteins and control nuclear proteins.
• Kinase activity assays and in vitro phosphorylation studies.
• Splicing assays using an E1A minigene.

Main Results:

• Endogenous PSKH1 localizes to SFCs, with its migration enhanced by co-expression of SR proteins.
• Overexpression of PSKH1 causes redistribution of SR proteins within the nucleus, independent of its kinase activity.
• PSKH1 associates with SFCs via its catalytic and C-terminal domains, but does not directly phosphorylate SR proteins.
• PSKH1 expression stimulates distal splicing of the E1A minigene.

Conclusions:

• PSKH1 and SR proteins exhibit a mutual relationship, with SR proteins targeting PSKH1 to SFCs.
• PSKH1 influences nuclear dynamics and the function of SR proteins, likely through indirect mechanisms.
• These findings shed light on the regulation of splicing factor organization and pre-mRNA splicing.