Yet another job for Dna2: Checkpoint activation

• Published in: DNA repair Vol. 32; pp. 17 - 23
• Main Authors: Wanrooij, Paulina H., Burgers, Peter M.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.08.2015
• Subjects: Ataxia Telangiectasia Mutated Proteins - genetics; Ataxia Telangiectasia Mutated Proteins - metabolism; ATR; Cell Cycle Checkpoints - genetics; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; DNA - chemistry; DNA - metabolism; DNA Breaks, Double-Stranded; DNA Helicases - genetics; DNA Helicases - metabolism; DNA Repair; DNA Replication; DNA, Fungal - chemistry; DNA, Fungal - metabolism; Dna2; Gene Expression Regulation, Fungal; Humans; Intracellular Signaling Peptides and Proteins - genetics; Intracellular Signaling Peptides and Proteins - metabolism; Mec1; Nuclease; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - metabolism; Replication checkpoint; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; FEN1; RPA; Mec1; 9–1–1; Replication checkpoint; DSB; ATM; Dna2; Nuclease; PIKK; ATRIP; dsDNA; ssDNA; ATR; NTD
• ISSN: 1568-7864; 1568-7856
• DOI: 10.1016/j.dnarep.2015.04.009

Mec1 (ATR in humans) is the principal kinase responsible for checkpoint activation in response to replication stress and DNA damage in Saccharomyces cerevisiae. Checkpoint initiation requires stimulation of Mec1 kinase activity by specific activators. The complexity of checkpoint initiation in yeast increases with the complexity of chromosomal states during the different phases of the cell cycle. In G1 phase, the checkpoint clamp 9–1–1 is both necessary and sufficient for full activation of Mec1 kinase whereas in G2/M, robust checkpoint function requires both 9–1–1 and the replisome assembly protein Dpb11 (human TopBP1). A third activator, Dna2, is employed specifically during S phase to stimulate Mec1 kinase and to initiate the replication checkpoint. Dna2 is an essential nuclease–helicase that is required for proper Okazaki fragment maturation, for double-strand break repair, and for protecting stalled replication forks. Remarkably, all three Mec1 activators use an unstructured region of the protein, containing two critically important aromatic residues, in order to activate Mec1. A role for these checkpoint activators in channeling aberrant replication structures into checkpoint complexes is discussed.