PMID:21878356

Citation	Ruhanen, H, Ushakov, K and Yasukawa, T (2011) Involvement of DNA ligase III and ribonuclease H1 in mitochondrial DNA replication in cultured human cells. Biochim. Biophys. Acta 1813:2000-7
Abstract	Recent evidence suggests that coupled leading and lagging strand DNA synthesis operates in mammalian mitochondrial DNA (mtDNA) replication, but the factors involved in lagging strand synthesis are largely uncharacterised. We investigated the effect of knockdown of the candidate proteins in cultured human cells under conditions where mtDNA appears to replicate chiefly via coupled leading and lagging strand DNA synthesis to restore the copy number of mtDNA to normal levels after transient mtDNA depletion. DNA ligase III knockdown attenuated the recovery of mtDNA copy number and appeared to cause single strand nicks in replicating mtDNA molecules, suggesting the involvement of DNA ligase III in Okazaki fragment ligation in human mitochondria. Knockdown of ribonuclease (RNase) H1 completely prevented the mtDNA copy number restoration, and replication intermediates with increased single strand nicks were readily observed. On the other hand, knockdown of neither flap endonuclease 1 (FEN1) nor DNA2 affected mtDNA replication. These findings imply that RNase H1 is indispensable for the progression of mtDNA synthesis through removing RNA primers from Okazaki fragments. In the nucleus, Okazaki fragments are ligated by DNA ligase I, and the RNase H2 is involved in Okazaki fragment processing. This study thus proposes that the mitochondrial replication system utilises distinct proteins, DNA ligase III and RNase H1, for Okazaki fragment maturation.
Links	PubMed PMC3223524 Online version:10.1016/j.bbamcr.2011.08.008
Keywords	Blotting, Southern; Blotting, Western; Bone Neoplasms/genetics; Bone Neoplasms/metabolism; DNA/genetics; DNA/metabolism; DNA Ligases/genetics; DNA Ligases/metabolism; DNA Replication; DNA, Mitochondrial/genetics; Flap Endonucleases/genetics; Flap Endonucleases/metabolism; Humans; Osteosarcoma/genetics; Osteosarcoma/metabolism; Ribonuclease H/genetics; Ribonuclease H/metabolism; Thymidine Kinase/deficiency; Tumor Cells, Cultured
edit table

Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
HUMAN:DNLI3		GO:0090298: negative regulation of mitochondrial DNA replication	ECO:0000315:		P		Fig. 1 B,C. DNA ligase III levels in cell lysates prepared from cells treated with scramble (Sc) dsRNA or DNA ligase III-specific (LIII) dsRNA.	complete CACAO 9375
HUMAN:DNLI3	involved_in	GO:0090298: negative regulation of mitochondrial DNA replication	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

References

See Help:References for how to manage references in GONUTS.