TFB2M is a mitochondrial transcription initiation factor essential for human mtDNA transcription and replication. TFB2M functions as a component of the mitochondrial transcription initiation complex alongside TFAM and POLRMT 1. Within this complex, TFB2M induces critical structural changes in POLRMT to enable promoter opening and stabilization of the transcription bubble 23. Specifically, TFB2M's non-template stabilizing loop (K153LDPRSGGVIKPP165) and tyrosine 209 interact with the non-template strand to facilitate start site selection at the +1 position 3. TFB2M also possesses S-adenosyl-L-methionine-dependent rRNA methyltransferase activity and may methylate specific adenosines in 12S mitochondrial rRNA. Notably, TFB2M stimulates transcription independently of its methyltransferase function 2. Beyond transcription, TFB2M is indispensable for mtDNA maintenance, as knockout of TFB2M results in complete mtDNA loss, demonstrating its role in both strand-asynchronous and strand-coupled replication initiation 4. TFB2M cannot be functionally compensated by its paralog TFB1M 4. These findings establish TFB2M as a critical regulator of mitochondrial bioenergetics through control of mtDNA gene expression and genome stability.