This gene encodes a serine/arginine protein kinase specific for the SR (serine/arginine-rich domain) family of splicing factors. The protein localizes to the nucleus and the cytoplasm. It is thought to play a role in regulation of both constitutive and alternative splicing by regulating intracellular localization of splicing factors. Alternative splicing of this gene results in multiple transcript variants. Additional alternatively spliced transcript variants have been described for this gene, but their full length nature have not been determined.[provided by RefSeq, Jul 2010],
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Function:
Catalytic activity:ATP + a protein = ADP + a phosphoprotein.,cofactor:Magnesium.,enzyme regulation:Activated by phosphorylation on Ser-51 and Ser-555.,Function:Plays a central role in the regulatory network for splicing, controlling the intranuclear distribution of splicing factors in interphase cells and the reorganization of nuclear speckles during mitosis. Hyperphosphorylates RS domain-containing proteins such as SFRS1 and SFRS2 on serine residues during metaphase but at lower levels during interphase. Locks onto SFRS1 to form a stable complex and processively phosphorylates the RS domain. Appears to mediate HBV core protein phosphorylation which is a prerequisite for pregenomic RNA encapsidation into viral capsids.,similarity:Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family.,similarity:Contains 1 protein kinase domain.,subunit:Present in a seven component complex, the toposome, which separates entangled circular chromatin DNA during chromosome segregation. The extended N-terminal domain of isoform 1 binds to the nuclear scaffold-associated protein SAFB suggesting this isoform may phosphorylate splicing factors in close vicinity to the nuclear matrix.,tissue specificity:Isoform 2 is predominantly expressed in the testis but is also present at lower levels in heart, ovary, small intestine, liver, kidney, pancreas and skeletal muscle. Isoform 1 is only seen in the testis, at lower levels than isoform 2.,
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Cellular Localization:
[Isoform 2]: Cytoplasm. Nucleus. Nucleus matrix. Microsome. Shuttles between the nucleus and the cytoplasm. Inhibition of the Hsp90 ATPase activity, osmotic stress and interaction with HHV-1 ICP27 protein can induce its translocation to the nucleus. KAT5/TIP60 inhibits its nuclear translocation.; [Isoform 1]: Cytoplasm. Nucleus matrix. Microsome. Mainly localized in the microsomal fraction and the cytoplasm, and to a lesser extent in the nuclear matrix.; Cytoplasm . Nucleus, nucleoplasm . Nucleus speckle . Chromosome . Preferentially localizes to the promoter of gene coding regions. .
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Tissue Expression:
Isoform 2 is predominantly expressed in the testis but is also present at lower levels in heart, ovary, small intestine, liver, kidney, pancreas and skeletal muscle. Isoform 1 is only seen in the testis, at lower levels than isoform 2. Highly expressed in different erythroid and lymphoid cell lines, with isoform 2 being far more abundant than isoform 1.