Serine/arginine-rich protein-specific kinase which specifically phosphorylates its substrates at serine residues located in regions rich in arginine/serine dipeptides, known as RS domains and is involved in the phosphorylation of SR splicing factors and the regulation of splicing ( ). Promotes neuronal apoptosis by up-regulating cyclin-D1 (CCND1) expression . This is done by the phosphorylation of SRSF2, leading to the suppression of p53/TP53 phosphorylation thereby relieving the repressive effect of p53/TP53 on cyclin-D1 (CCND1) expression . Phosphorylates ACIN1, and redistributes it from the nuclear speckles to the nucleoplasm, resulting in cyclin A1 but not cyclin A2 up-regulation . Plays an essential role in spliceosomal B complex formation via the phosphorylation of DDX23/PRP28 . Probably by phosphorylating DDX23, leads to the suppression of incorrect R-loops formed during transcription; R-loops are composed of a DNA:RNA hybrid and the associated non-template single-stranded DNA . Can mediate hepatitis B virus (HBV) core protein phosphorylation . Plays a negative role in the regulation of HBV replication through a mechanism not involving the phosphorylation of the core protein but by reducing the packaging efficiency of the pregenomic RNA (pgRNA) without affecting the formation of the viral core particles .
Subcellular locations: Cytoplasm, Nucleus, Nucleoplasm, Nucleus speckle, Chromosome
Shuttles between the nucleus and the cytoplasm ( ). KAT5/TIP60 inhibits its nuclear translocation . Phosphorylation at Thr-492 by PKB/AKT1 promotes nuclear translocation . Preferentially localizes across the entire gene coding region . During transcription, accumulates at chromatin loci where unscheduled R-loops form and colocalizes with paused 'Ser-5'-phosphorlyated POLR2A/RNA polymerase II and helicase DDX23 .
Highly expressed in brain, moderately expressed in heart and skeletal muscle and at low levels in lung, liver, and kidney.