title: Primer release is the rate-limiting event in lagging-strand synthesis mediated by the T7 replisome.
abstract: DNA replication occurs semidiscontinuously due to the antiparallel DNA strands and polarity of enzymatic DNA synthesis. Although the leading strand is synthesized continuously, the lagging strand is synthesized in small segments designated Okazaki fragments. Lagging-strand synthesis is a complex event requiring repeated cycles of RNA primer synthesis, transfer to the lagging-strand polymerase, and extension effected by cooperation between DNA primase and the lagging-strand polymerase. We examined events controlling Okazaki fragment initiation using the bacteriophage T7 replication system. Primer utilization by T7 DNA polymerase is slower than primer formation. Slow primer release from DNA primase allows the polymerase to engage the complex and is followed by a slow primer handoff step. The T7 single-stranded DNA binding protein increases primer formation and extension efficiency but promotes limited rounds of primer extension. We present a model describing Okazaki fragment initiation, the regulation of fragment length, and their implications for coordinated leading- and lagging-strand DNA synthesis.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
authors.forename: Alfredo J
authors.initials: AJ
authors.lastname: Hernandez
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
authors.forename: Seung-Joo
authors.initials: SJ
authors.lastname: Lee
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115 ccr@hms.harvard.edu.
authors.forename: Charles C
authors.initials: CC
authors.lastname: Richardson
mesh_terms: D017123:Bacteriophage T7 / Q000502:physiology*; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication / Q000502:physiology*; D004279:DNA, Viral / Q000096:biosynthesis* / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D008954:Models, Biological
chemical_list: D004279:DNA, Viral; C022262:Okazaki fragments; D004247:DNA; C034970:bacteriophage T7 induced DNA polymerase; D004259:DNA-Directed DNA Polymerase
keywords: DNA primase; Okazaki fragment; primer; replisome