RBMX (RNA binding motif protein X-linked) is a nuclear RNA-binding protein that regulates multiple aspects of RNA processing and transcriptional control. The protein functions as a key splicing regulator, controlling alternative splicing of various pre-mRNAs and participating in supraspliceosome complexes 1. RBMX directly binds to RNA sequences and can either activate or suppress exon inclusion, demonstrating its dual regulatory capacity in splicing control 1. Beyond splicing, RBMX plays crucial roles in maintaining genomic stability by assembling ribonucleoprotein complexes, notably the NORAD-activated ribonucleoprotein complex 1 (NARC1) which contains topoisomerase I and other DNA repair proteins 2. The protein also functions as a transcriptional regulator, directly controlling CBX5 expression to maintain chrX state in myeloid leukemia cells 3. RBMX exhibits tissue-specific functions, with retroposed copies showing testis-specific expression patterns that may compensate for X-inactivation in male germ cells 4. Post-translational modifications, particularly SUMOylation, regulate RBMX function in exosomal miRNA sorting, impacting disease progression in diabetic kidney disease 5. In cancer contexts, RBMX can function as a tumor suppressor, inhibiting bladder cancer cell proliferation and glycolysis by downregulating PKM2 6, while also being implicated in chrX lymphocytic leukemia metabolism through circRNA regulation 7.