FASTK (Fas-activated serine/threonine kinase) is a multifunctional RNA-binding protein with distinct mitochondrial and cytoplasmic isoforms that regulate gene expression at multiple levels 1. The mitochondrial variant of FASTK is essential for post-transcriptional regulation of mitochondrial mRNA metabolism, particularly stabilizing ND6 (NADH dehydrogenase complex I subunit 6) mRNA through binding at multiple sites along the transcript and cooperating with the mitochondrial degradosome 2. FASTK binds preferentially to single-stranded, G-rich RNA sequences, including G-quadruplex-forming structures, protecting mitochondrial mRNAs from degradation 3. Loss of FASTK expression results in specific ND6 mRNA depletion and reduced complex I activity, indicating its critical role in oxidative phosphorylation 2. Beyond mitochondrial function, FASTK participates in alternative splicing regulation and apoptotic signaling 4. Disease relevance includes alcoholic liver disease, where FASTK deletion ameliorates hepatic damage by preserving SIRT1 mRNA stability through modulation of HuR-mediated mRNA regulation 5. FASTK alterations occur frequently in multiple cancers, with amplifications in ovarian and lung cancers and mutations in uterine cancers and melanomas, suggesting potential diagnostic and therapeutic significance 6.