PPP4R2 is a regulatory subunit of protein phosphatase 4 (PPP4C) that functions as a key modulator of multiple cellular processes. Structurally, PPP4R2 comprises 453 amino acids and forms inactive 450-600 kDa complexes with PPP4C at centrosomal microtubule organizing centers, where it targets and regulates PPP4C activity 1. PPP4R2 plays a critical role in DNA damage response by recruiting PPP4C to dephosphorylate gamma-H2AX and RPA2, facilitating RAD51-mediated homologous recombination repair 2. Beyond DNA repair, PPP4R2 functionally cooperates with the SMN complex to regulate spliceosomal snRNP maturation and modulates circadian clock dynamics by controlling CLOCK/BMAL1 phosphorylation status 34. In neuronal cells, PPP4R2 promotes motor neuron differentiation and protects against DNA damage-induced apoptosis, suggesting why PPP4R2 deficiency specifically impacts motor neuron viability 3. Disease relevance includes acute myeloid leukemia, where PPP4R2 deletions impair DNA damage response protein dephosphorylation and correlate with reduced expression in primary samples 2. Germline variants in PPP4R2 associate with chr3 lymphocytic leukemia treatment need and survival outcomes 5, while GWAS identified PPP4R2 loci in Alzheimer's disease biomarker studies 6. These findings establish PPP4R2 as a multifunctional regulatory protein essential for DNA repair, neuronal development, and disease progression.