High impact information on DNA2

• Here we show that the endonucleases Dna2 and Fen1 act sequentially to facilitate the complete removal of the primer RNA [1].
• For example, the DNA-binding domain of the yeast GAL4 protein interacts very poorly with nucleosome cores compared with naked DNA2 (and see below), and binding of other activators is even more strongly inhibited [2].
• The human Bloom syndrome gene suppresses the DNA replication and repair defects of yeast dna2 mutants [3].
• The DNA2 gene was cloned by complementation of the dna2ts gene phenotype [4].
• Specifically, we show that deletion of PIF1 suppresses the lethality of a DNA2-null mutant [5].

Biological context of DNA2

• This gene is identical to DNA2, encoding a helicase required for DNA replication [6].
• DNA2 alleles were isolated that cause either temperature sensitivity, sensitivity to alkylation damage, or both [7].
• Temperature-shift experiments indicate that Dna2p functions during late S phase, although dna2 mutants are not deficient in bulk DNA synthesis [6].
• Frequencies of mitotic recombination and chromosome loss are elevated in dna2 mutants, also supporting a role for the protein in DNA synthesis [6].
• As with its role in cell cycle progression, both the N-terminal and C-terminal regions, as well as the kinase domain of Tor1p, are required for rescue of dna2 mutants [6].

Anatomical context of DNA2

• The ribosomal DNA locus and the nucleolus seem to be particularly sensitive to defects in dna2 mutants, although in dna2 mutants extrachromosomal ribosomal circles do not accumulate during the aging of a mother cell [8].

Associations of DNA2 with chemical compounds

• The Dna2p is also distributed throughout the nucleus in cells growing in the presence of double-strand-break-inducing agents such as bleomycin [9].
• Like FEN1, Dna2p can track over substrates with a non-Watson Crick base, such as a biotin, or a missing base within a chain [10].
• Both the helicase and nuclease activities of Dna2Pho were inhibited by substrates with RNA segments at the 5'-end of flap DNA, whereas the nuclease activity of Dna2 from S. cerevisiae was reported to be stimulated by RNA segments in the 5'-tail (Bae, S.-H., and Seo, Y. S. (2000) J. Biol. Chem. 38022-38031) [11].

Physical interactions of DNA2

• Dna2 was recently shown to dissociate flap-bound RPA, independent of cleavage [12].

Regulatory relationships of DNA2

• The Saccharomyces cerevisiae DNA2 gene encodes a DNA-stimulated ATPase and DNA helicase/nuclease essential for DNA replication [13].
• In agreement with these results, the proposed generation of double strand breaks in pol3-exo(-) rad27 mutants was suppressed by the overexpression of DNA2 [14].

Other interactions of DNA2

• Full activity of the Dna2 helicase function is therefore not needed for viability, but is required for repairing damage and for tolerating loss of Ctf4 [7].
• The X-ray sensitivity of dna2 mutants is suppressed by overexpression of a 5' to 3' exonuclease, the yeast FEN-1 structure-specific nuclease, encoded by the RAD27 gene, which also suppresses the growth defect of dna2-ts mutants [13].
• SGS1 encodes a helicase with similar properties to Dna2 protein [13].
• In addition, we identified physical and functional interactions between these proteins and found that RPA binds Dna2 predominantly through its large subunit, Rpa1 [15].
• Arrest of dna2 mutants was RAD9 dependent, but deleting this checkpoint resulted in either no effect or suppression of defects, including the synthetic lethality with ctf4 [7].

Analytical, diagnostic and therapeutic context of DNA2

• Both chromatin immunoprecipitation (ChIP) and immunofluorescence show that Dna2p associates with telomeres but not bulk chromosomal DNA in G(1) phase, when there is no telomere replication and the telomere is transcriptionally silenced [9].
• Moreover, they all interacted with S. pombe Dna2 in a yeast two-hybrid assay, albeit to different extents [16].

References