CLP1 is a polynucleotide kinase that phosphorylates 5'-hydroxyl groups of double-stranded and single-stranded RNA and DNA, with particular efficiency toward dsRNA 1. It serves two critical cellular functions: tRNA splicing and mRNA 3'-end processing. In tRNA splicing, CLP1 phosphorylates the 5'-terminus of the tRNA 3'-exon within the tRNA splicing endonuclease (TSEN) complex, a prerequisite for ligation of exon halves and mature tRNA production 12. CLP1 also participates in mRNA 3'-end formation as a component of cleavage complex II 3. Additionally, CLP1 phosphorylates exogenous siRNAs, facilitating their RISC incorporation, though endogenous siRNAs generated by DICER1 cleavage are already 5'-phosphorylated 4. CLP1 is essential for cerebellar development; kinase-dead or mutant CLP1 causes microcephaly, reduced cortical volume, and neuronal progenitor cell death 12. Mutations in CLP1 disrupt TSEN complex stability and pre-tRNA cleavage, leading to immature tRNA accumulation 12. These defects manifest as pontocerebellar hypoplasia, characterized by neurodegeneration, underdevelopment of specific brain regions, motor-sensory defects, and cortical dysgenesis 15. CLP1's role in tRNA biogenesis is critical for both peripheral and central nervous system function.