RT Journal Article SR Electronic T1 Unexpected sequences and structures of mtDNA required for efficient transcription from the first heavy-strand promoter JF bioRxiv FD Cold Spring Harbor Laboratory SP 129908 DO 10.1101/129908 A1 Akira Uchida A1 Divakaran Murugesapillai A1 Yao Wang A1 Maria F. Lodeiro A1 Shaan Prabhakar A1 Jamie J. Arnold A1 L. James Maher III A1 Mark C. Williams A1 Craig E. Cameron YR 2017 UL http://biorxiv.org/content/early/2017/04/24/129908.abstract AB Human mtDNA contains three promoters, suggesting a need for differential expression of the mitochondrial genome. Studies of mitochondrial transcription have used a reductionist approach, perhaps masking differential regulation. Here we evaluate transcription from light-strand (LSP) and heavy-strand (HSP1) promoters using templates that mimic their natural context. These studies reveal sequences upstream, hypervariable in the human population (HVR3), and downstream of the HSP1 transcription start site required for maximal yield. The carboxy-terminal tail of TFAM is essential for activation of HSP1 but not LSP. Images of the template obtained by atomic force microscopy show that TFAM creates loops in a discrete region, the formation of which correlates with activation of HSP1; looping is lost in tail-deleted TFAM. Identification of HVR3 as a transcriptional regulatory element may contribute to between-individual variability in mitochondrial gene expression. The unique requirement of HSP1 for the TFAM tail may enable its regulation by post-translational modifications.