The mitochondrial single-stranded DNA binding protein is essential for initiation of mtDNA replication
Min Jiang, Xie Xie, Xuefeng Zhu, Shan Jiang, Dusanka Milenkovic, Jelena Misic, Yonghong Shi, Nirwan Tandukar, Xinping Li, Ilian Atanassov, Louise Jenninger, Emily Hoberg, Sara Albarran-Gutierrez, Zsolt Szilágyi, Bertil Macao, Stefan J. Siira, Valério Carelli, Jack D. Griffith, Claes M. Gustafsson, Thomas J. Nicholls, Aleksandra Filipovska, Nils‐Göran Larsson, Maria Falkenberg
Abstract
We report a role for the mitochondrial single-stranded DNA binding protein (mtSSB) in regulating mitochondrial DNA (mtDNA) replication initiation in mammalian mitochondria. Transcription from the light-strand promoter (LSP) is required both for gene expression and for generating the RNA primers needed for initiation of mtDNA synthesis. In the absence of mtSSB, transcription from LSP is strongly up-regulated, but no replication primers are formed. Using deep sequencing in a mouse knockout model and biochemical reconstitution experiments with pure proteins, we find that mtSSB is necessary to restrict transcription initiation to optimize RNA primer formation at both origins of mtDNA replication. Last, we show that human pathological versions of mtSSB causing severe mitochondrial disease cannot efficiently support primer formation and initiation of mtDNA replication.