Mitochondrial RNA polymerase is needed for activation of the origin of light-strand DNA replication.

TitleMitochondrial RNA polymerase is needed for activation of the origin of light-strand DNA replication.
Publication TypeJournal Article
Year of Publication2010
AuthorsFusté, JMiralles, Wanrooij, S, Jemt, E, Granycome, CE, Cluett, TJ, Shi, Y, Atanassova, N, Holt, IJ, Gustafsson, CM, Falkenberg, M
JournalMol Cell
Date Published2010 Jan 15
KeywordsDNA Replication, DNA, Mitochondrial, DNA-Directed RNA Polymerases, Gene Silencing, Humans, Models, Genetic, Nucleic Acid Conformation, Poly T, Replication Origin

Mitochondrial DNA is replicated by a unique enzymatic machinery, which is distinct from the replication apparatus used for copying the nuclear genome. We examine here the mechanisms of origin-specific initiation of lagging-strand DNA synthesis in human mitochondria. We demonstrate that the mitochondrial RNA polymerase (POLRMT) is the primase required for initiation of DNA synthesis from the light-strand origin of DNA replication (OriL). Using only purified POLRMT and DNA replication factors, we can faithfully reconstitute OriL-dependent initiation in vitro. Leading-strand DNA synthesis is initiated from the heavy-strand origin of DNA replication and passes OriL. The single-stranded OriL is exposed and adopts a stem-loop structure. At this stage, POLRMT initiates primer synthesis from a poly-dT stretch in the single-stranded loop region. After about 25 nt, POLRMT is replaced by DNA polymerase gamma, and DNA synthesis commences. Our findings demonstrate that POLRMT can function as an origin-specific primase in mammalian mitochondria.

Alternate JournalMol. Cell
Citation Key10.1016/j.molcel.2009.12.021
PubMed ID20129056
Grant ListMC_U105663140 / / Medical Research Council / United Kingdom