title: Regulation of DNA replication at the end of the mitochondrial D-loop involves the helicase TWINKLE and a conserved sequence element.
abstract: The majority of mitochondrial DNA replication events are terminated prematurely. The nascent DNA remains stably associated with the template, forming a triple-stranded displacement loop (D-loop) structure. However, the function of the D-loop region of the mitochondrial genome remains poorly understood. Using a comparative genomics approach we here identify two closely related 15 nt sequence motifs of the D-loop, strongly conserved among vertebrates. One motif is at the D-loop 5'-end and is part of the conserved sequence block 1 (CSB1). The other motif, here denoted coreTAS, is at the D-loop 3'-end. Both these sequences may prevent transcription across the D-loop region, since light and heavy strand transcription is terminated at CSB1 and coreTAS, respectively. Interestingly, the replication of the nascent D-loop strand, occurring in a direction opposite to that of heavy strand transcription, is also terminated at coreTAS, suggesting that coreTAS is involved in termination of both transcription and replication. Finally, we demonstrate that the loading of the helicase TWINKLE at coreTAS is reversible, implying that this site is a crucial component of a switch between D-loop formation and full-length mitochondrial DNA replication.
authors.affiliation: Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Jemt
authors.affiliation: Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden.
authors.forename: Örjan
authors.initials: Ö
authors.lastname: Persson
authors.affiliation: Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden.
authors.forename: Yonghong
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden.
authors.forename: Majda
authors.initials: M
authors.lastname: Mehmedovic
authors.affiliation: Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden.
authors.forename: Jay P
authors.initials: JP
authors.lastname: Uhler
authors.affiliation: Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden.
authors.forename: Marcela
authors.initials: M
authors.lastname: Dávila López
authors.affiliation: Department of Laboratory Medicine, Karolinska Institutet, Retzius väg 8, 171 77 Stockholm, Sweden.
authors.forename: Christoph
authors.initials: C
authors.lastname: Freyer
authors.affiliation: Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden.
authors.forename: Claes M
authors.initials: CM
authors.lastname: Gustafsson
authors.affiliation: Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden tore.samuelsson@medkem.gu.se.
authors.forename: Tore
authors.initials: T
authors.lastname: Samuelsson
authors.affiliation: Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden maria.falkenberg@medkem.gu.se.
authors.forename: Maria
authors.initials: M
authors.lastname: Falkenberg
mesh_terms: D000818:Animals; D001483:Base Sequence; D017124:Conserved Sequence; D004265:DNA Helicases / Q000378:metabolism*; D004261:DNA Replication; D004272:DNA, Mitochondrial / Q000096:biosynthesis* / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D055029:Inverted Repeat Sequences; D051379:Mice; D024101:Mitochondrial Proteins / Q000378:metabolism*; D059372:Nucleotide Motifs; D020733:RNA, Small Cytoplasmic / Q000737:chemistry / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D018271:Signal Recognition Particle / Q000737:chemistry / Q000235:genetics; D061806:Transcription Termination, Genetic; D014714:Vertebrates / Q000235:genetics
chemical_list: C115990:7SL RNA; D004272:DNA, Mitochondrial; D024101:Mitochondrial Proteins; D020733:RNA, Small Cytoplasmic; D018271:Signal Recognition Particle; D004265:DNA Helicases; C431576:TWNK protein, human