9MN4

Structure of the human mitochondrial initially transcribing complex, IC3

Summary for 9MN4

• Entry DOI: 10.2210/pdb9mn4/pdb
• EMDB information: 48412
• Descriptor: Transcription factor A, mitochondrial, Dimethyladenosine transferase 2, mitochondrial, DNA-directed RNA polymerase, mitochondrial, ... (6 entities in total)
• Functional Keywords: mitochondrial rna polymerase, transcription initiation complex, transcription, polrmt, transcription-dna-rna complex
• Biological source: Homo sapiens (human); More
• Total number of polymer chains: 6
• Total formula weight: 251264.06

Authors

Herbine, K.H.,Nayak, A.R.,Temiakov, D. (deposition date: 2024-12-20, release date: 2025-08-06, Last modification date: 2025-09-03)

Primary citation

Herbine, K.,Nayak, A.R.,Zamudio-Ochoa, A.,Temiakov, D.
Structural basis for promoter recognition and transcription factor binding and release in human mitochondria.
Mol.Cell, 85:3123-3136.e7, 2025

PubMed Abstract: Transcription in human mitochondria is driven by a core apparatus consisting of a Pol A family RNA polymerase (mtRNAP), the initiation factors TFAM and TFB2M, and the elongation factor TEFM. While earlier structures of initiation and elongation complexes provided valuable snapshots, they represent isolated stages of a highly dynamic and multistep process. Critical aspects of mitochondrial transcription-such as DNA recognition and melting, promoter escape, and the release of initiation factors-remain poorly understood. Here, we present a series of cryoelectron microscopy (cryo-EM) structures that capture the transcription complex as it transitions from the initial open promoter complex to the processive elongation complex through intermediate stages. Our data reveal new, previously unidentified determinants of promoter specificity: the sequential disengagement of mtRNAP from TFAM and the promoter, the release of TFB2M, and the recruitment of TEFM. Together, these findings provide a detailed molecular mechanism underlying transcription in human mitochondria.

PubMed: 40712587
DOI: 10.1016/j.molcel.2025.06.016

Experimental method

ELECTRON MICROSCOPY (3.05 Å)