Folding the message: mRNA structure as a regulatory layer of human mitochondrial gene expression.

Mammalian mitochondrial gene expression operates within an unusually compact genomic architecture in which most regulatory information must be encoded within or immediately adjacent to protein-coding sequences. In this context, mitochondrial mRNAs function not merely as templates for translation but as structured molecules whose folding landscape contributes to multiple stages of gene expression. Recent advances in chemical probing, mutational profiling, and mitoribosome profiling have begun to disclose the human mitochondrial mRNA structurome in its native organellar context, revealing a transcriptome that is broadly accessible yet punctuated by localized structural elements and alternative conformational states. These studies indicate that RNA structure contributes to translation initiation on leaderless transcripts, elongation kinetics, translational coupling across bicistronic junctions, and dynamic remodeling during membrane protein synthesis. They also highlight the role of RNA-binding proteins, including LRPPRC-SLIRP and related factors, in maintaining a translation-competent folding environment. In this review, we discuss the structural organization of mitochondrial mRNAs, the experimental approaches that enabled its analysis, and emerging mechanistic links between RNA folding, translational regulation, and respiratory chain biogenesis. We further discuss how alterations in mt-mRNA structure may represent an underappreciated determinant of mitochondrial disease and consider implications for future diagnostic and therapeutic strategies.