PAIP2 (poly(A) binding protein interacting protein 2) functions as a translation repressor that negatively regulates translation initiation by competing with PAIP1 for binding to PABPC1 1. PAIP2 contains two distinct binding sites for PABP, enabling formation of a trimeric complex with one PABP molecule and two PAIP2 molecules at nanomolar to micromolar affinities 1. Mechanistically, PAIP2 displaces PABPC1 from poly(A) RNA and disrupts mRNA circularization, a process critical for translation initiation 1. PAIP2 also regulates translation termination by preventing PABP-mediated activation of eRF3 at premature termination codons 2. Beyond cytoplasmic functions, PAIP2 localizes to active gene promoters in the nucleus where it is loaded onto nascent mRNA co-transcriptionally 3. Clinically, PAIP2 regulates vascular endothelial growth factor (VEGF) mRNA stability through direct 3'-UTR binding and cooperation with HuR, influencing angiogenesis 4. PAIP2 also functions as an innate antiviral factor, restricting cytomegalovirus replication by limiting translation initiation factor assembly 5. PAIP2 protein stability is controlled by the E3 ubiquitin ligase EDD in a PABPC1-dependent manner, providing homeostatic feedback 6. Pathogenic variants in PABPC1 that impair PAIP2 binding cause developmental delay and autism spectrum features, highlighting the importance of PABPC1-PAIP2 interactions in neurogenesis 7.