Okazaki fragments contain an initiator RNA/DNA primer that must be removed before the fragments are joined. In eukaryotes, the primer region is raised into a flap by the strand displacement activity of DNA polymerase delta. The Dna2 helicase/nuclease and then flap endonuclease 1 (FEN1) are proposed to act sequentially in flap removal. Dna2 and FEN1 both employ a tracking mechanism to enter the ...

In both budding and fission yeasts, a null mutation of the DNA2 gene is lethal. In contrast, a null mutation of Caenorhabditis elegans dna2+ causes a delayed lethality, allowing survival of some mutant C.elegans adults to F2 generation. In order to understand reasons for this difference in requirement of Dna2 between these organisms, we examined the enzymatic properties of the recombinant C.ele...

Dna2 was first characterized in yeast as an essential gene encoding a protein with both helicase and endonuclease activities involved in maturation of Okazaki fragments during DNA replication. Dna2 also plays a role in double-strand break (DSB) repair by homolo-gous recombination. The respective contributions of its replication and/or repair functions toward cell viability and resistance to gen...

During DNA replication, synthesis of the lagging strand occurs in stretches termed Okazaki fragments. Before adjacent fragments are ligated, any flaps resulting from the displacement of the 5' DNA end of the Okazaki fragment must be cleaved. Previously, Dna2 was implicated to function upstream of flap endonuclease 1 (Fen1 or Rad27) in the processing of long flaps bound by the replication protei...

The polyguanine-rich DNA sequences commonly found at telomeres and in rDNA arrays have been shown to assemble into structures known as G quadruplexes, or G4 DNA, stabilized by base-stacked G quartets, an arrangement of four hydrogen-bonded guanines. G4 DNA structures are resistant to the many helicases and nucleases that process intermediates arising in the course of DNA replication and repair....

Homologous recombination plays a key role in the repair of double-strand breaks (DSBs), and thereby significantly contributes to cellular tolerance to radiotherapy and some chemotherapy. DSB repair by homologous recombination is initiated by 5' to 3' strand resection (DSB resection), with nucleases generating the 3' single-strand DNA (3'ssDNA) at DSB sites. Genetic studies of Saccharomyces cere...

The human DNA2 (DNA replication helicase/nuclease 2) protein is expressed in both the nucleus and mitochondria, where it displays ATPase-dependent nuclease and helicase activities. DNA2 plays an important role in the removing of long flaps in DNA replication and long-patch base excision repair (LP-BER), interacting with the replication protein A (RPA) and the flap endonuclease 1 (FEN1). DNA2 ca...

Processing of G4 DNA by Dna2 Helicase/Nuclease and RPA Provides Insights into the Mechanism of Dna2/RPA Substrate Recognition Taro Masuda-Sasa, Piotr Polaczek, Xiao P. Peng, Lu Chen and Judith L. Campbell Braun Laboratories, 147-75, California Institute of Technology, Pasadena, CA 91125 Running title: Dna2/RPA/G4 interactions

When replication forks stall at damaged bases or upon nucleotide depletion, the intra-S phase checkpoint ensures they are stabilized and can restart. In intra-S checkpoint-deficient budding yeast, stalling forks collapse, and ∼10% form pathogenic chicken foot structures, contributing to incomplete replication and cell death (Lopes et al., 2001; Sogo et al., 2002; Tercero and Diffley, 2001). Usi...

Dna2 is a nuclease/helicase with proposed roles in DNA replication, double-strand break repair and telomere maintenance. For each role Dna2 is proposed to process DNA substrates with a 50-flap. To date, however, Dna2 has not revealed a preference for binding or cleavage of flaps over single-stranded DNA. Using DNA binding competition assays we found that Dna2 has substrate structure specificity...