CLK3 (CDC-like kinase 3) is a dual-specificity kinase that phosphorylates both serine/threonine and tyrosine residues on SR (serine/arginine-rich) spliceosomal proteins, including SRSF1 and SRSF3 1. It regulates alternative RNA splicing and can redistribute SR proteins from nuclear speckles to diffuse nucleoplasmic localization, thereby controlling splicing patterns of genes like tissue factor (F3) in endothelial cells. Mechanistically, CLK3 phosphorylates USP13 at Y708, promoting c-Myc stabilization and activation of purine metabolic genes 1. CLK3 is also regulated by the DEAD-box ATPase DDX41, which controls CLK3 transcript splicing during myeloid differentiation 2. Clinically, CLK3 expression is significantly elevated in cholangiocarcinoma, with a recurrent gain-of-function Q607R mutation identified in the kinase domain 1. High CLK3 expression correlates with aberrant nucleotide metabolism reprogramming and disease progression. Additionally, CLK3-regulated mis-splicing events generate neoantigens in leukemias with SRSF2 mutations, creating targets for T cell immunotherapy 3. CLK3 represents a therapeutic target, with tacrine hydrochloride identified as a potential CLK3 inhibitor for cholangiocarcinoma treatment.