GRSF1 is an RNA-binding protein that primarily functions as a regulator of post-transcriptional gene expression in mitochondria and the nucleus. In mitochondria, GRSF1 binds G-rich RNA sequences and is required for mitochondrial ribosome assembly and recruitment of mRNAs and long non-coding RNAs, particularly ND6 mRNA and transcripts from the light strand of mtDNA 123. GRSF1 facilitates degradosome-mediated decay of non-coding mitochondrial transcripts by unwinding G-quadruplex RNA structures, enabling their degradation 3. Beyond mitochondrial function, GRSF1 regulates post-transcriptional stability of nuclear-encoded mRNAs. It stabilizes BCKDHB mRNA by directly binding G-tracts in its coding region, maintaining branched-chain amino acid homeostasis critical for cardiac function 4. GRSF1 also negatively regulates fibrinogen mRNA stability, antagonizing age-associated hypercoagulability 5. Additionally, GRSF1 controls nuclear export and translation of mitochondrial long non-coding RNA RMRP and influenza A virus nucleoprotein mRNAs 67. Clinically, GRSF1 downregulation is implicated in heart failure pathogenesis and cellular senescence. Loss of GRSF1 causes mitochondrial stress, increased ROS production, DNA damage, and pro-inflammatory responses 8. GRSF1 has been identified as a candidate disease gene in clinical genomics 9, and super-resolution microscopy techniques now enable visualization of GRSF1-associated mitochondrial mRNA distribution in health and disease states 10.