The Dna Replication Fork in Eukaryotic Cells

Abstract

Replication of the two template strands at eukaryotic cell DNA replication forks is a highly coordinated process that ensures accurate and efficient genome duplication. Biochemical studies, principally of plasmid DNAs containing the Simian Virus 40 origin of DNA replication, and yeast genetic studies have uncovered the fundamental mechanisms of replication fork progression. At least two different DNA polymerases, a single-stranded DNA-binding protein, a clamp-loading complex, and a polymerase clamp combine to replicate DNA. Okazaki fragment synthesis involves a DNA polymerase-switching mechanism, and maturation occurs by the recruitment of specific nucleases, a helicase, and a ligase. The process of DNA replication is also coupled to cell-cycle progression and to DNA repair to maintain genome integrity. CONTENTS

Evidence of cis-acting factors in replication-mediated trinucleotide repeat instability in primate cells

“…To investigate the role of primate DNA replication on TNR stability, we used the SV40 replication system that, in addition to being a model of the primate replication fork 28,29 , has been used to study replication fidelity 35 , DNA mutagenesis and DNA repair. Replication of SV40 plasmids in transfected cells uses both Tantigen and the replication machinery of the host cell.…”

“…Scale bar, 100 nm. , and their priming is coordinated with leading-strand synthesis 28,29 (Fig. 1a).…”

“…A detailed understanding of primate replication fork dynamics has been gained through the SV40 viral DNA replication system 28,29 . Each replication fork comprises a continuous leading strand and a discontinuous lagging strand, which consists of several Okazaki fragments each of roughly 135-145 nt (Fig.…”

“…Synthesis is complete on reaching the initiator RNA of the previous Okazaki fragment. The processing of Okazaki fragments involves removal of the RNA primer, gap filling and ligation 25,29 . An alternative, but not mutually exclusive model for the production of Okazaki fragments is the 'nested discontinuity model' (Fig.…”

Honey, I shrunk the DNA: DNA length as a probe for nucleic‐acid enzyme activity

“…78,79 The helicase unwinds the parental double-stranded DNA (dsDNA) into two DNA strands allowing two DNA polymerases, complexed with processivity factors, to each synthesize DNA on the two single-stranded templates. The 5 0 to 3 0 direction of polymerase-dependent nucleic-acid synthesis permits one of these enzymes to synthesize DNA in a continuous fashion on the leading strand.…”