SRPK1 Protein, Human (Active)

SRPK1, a serine/arginine-rich protein-specific kinase, exerts its regulatory influence by phosphorylating substrates at serine residues within arginine/serine-rich (RS) domains, notably targeting SR splicing factors to modulate splicing. This kinase assumes a pivotal role in the intricate splicing regulatory network, orchestrating the intranuclear distribution of splicing factors during interphase and orchestrating the reorganization of nuclear speckles during mitosis. Beyond splicing, SRPK1 extends its impact to diverse cellular activities, including mRNA maturation steps, chromatin reorganization in somatic and sperm cells, and cell cycle progression. Notably, isoform 2 of SRPK1 employs a sophisticated mechanism, involving both processive and distributive phosphorylation steps, when phosphorylating substrates like SRSF1. Furthermore, SRPK1 plays a role in hepatitis B virus (HBV) replication, where isoform 2 negatively regulates replication by affecting the packaging efficiency of pregenomic RNA (pgRNA) without directly phosphorylating the core protein. Additionally, SRPK1's involvement in the splicing of MAPT/TAU exon 10 underscores its multifaceted impact on cellular processes, with the isoform ratio influencing cell fate in contexts such as the K-562 leukaemic cell line, where isoform 2 promotes proliferation, while isoform 1 favors differentiation.