serine/threonine-protein kinase SRPK1; SFRS protein kinase 1; serine/arginine-rich protein-specific kinase 1; SR-protein-specific kinase 1 (SRPK1)

Function

• role in regulatory network for splicing
  • intranuclear distribution of splicing factors in interphase cells
  • reorganization of nuclear speckles during mitosis
• hyperphosphorylates RS domain-containing phosphoproteins such as SFRS1 & SFRS2 & ZRSR2 on Ser during metaphase, but at lower levels during interphase
  • locks onto SFRS1 to form a stable complex & phosphorylates the RS domain
• may phosphorylate splicing factors in close vicinity to the nuclear matrix.
• component of the toposome
• activated by phosphorylation on Ser-51 & Ser-555
• present in a seven component complex, the toposome, which separates entangled circular chromatin DNA during chromosome segregation

Cofactor: Mg+2

Structure

• belongs to the protein kinase superfamily, CMGC Ser/Thr protein kinase family
• contains 1 protein kinase domain

Compartment

cytoplasm. nucleus

Alternative splicing

• named isoforms=2
• at least one insoform may be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay

Expression

• isoform 2
  • predominantly expressed in the testis
  • also present at lower levels in heart, ovary, small intestine, liver, kidney, pancreas & skeletal muscle
• isoform 1
  • expressed only in testis
  • expressed at lower levels than isoform 2

Pathology

• mediates HBV core protein phosphorylation, a prerequisite for pregenomic RNA encapsidation into viral capsids
• interacts with HHV-1 ICP27 protein

More general terms

• serine/threonine kinase

Component of

• toposome

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=6732
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:6732
• OMIM: https://mirror.omim.org/entry/601939
• UniProt: http://www.uniprot.org/uniprot/Q96SB4.html