RPS4X encodes a ribosomal protein S4 that functions as a structural component of the small ribosomal subunit, playing essential roles in protein synthesis 1. The protein participates in ribosome biogenesis as part of the small subunit processome, where it associates with pre-rRNA and other factors to facilitate RNA folding, modifications, and cleavage during ribosome assembly 2. Beyond its canonical ribosomal function, RPS4X exhibits significant extraribosomal activities. It physically interacts with SLFN11 to regulate the mTOR signaling pathway, with reduced RPS4X-SLFN11 interaction promoting hepatocellular carcinoma tumorigenesis and metastasis 3. Additionally, RPS4X modulates the SCF ubiquitin ligase complex by disrupting Cullin1-Skp1 interactions, leading to stabilization of anti-apoptotic proteins MCL1 and HAX1, thereby enhancing cell survival and resistance to apoptosis 4. The gene shows tissue-specific upregulation in Alzheimer's disease brain capillaries, suggesting involvement in cerebrovascular pathology 5. As an X-linked gene that escapes X-chromosome X, RPS4X may contribute to Turner syndrome phenotypes and exhibits sex-specific expression patterns in human skeletal muscle cells 67. RPS4X also serves as a target for HPV integration in cervical cancer progression 8.