Wanrooij Paulina H, Burgers Peter M
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
DNA Repair (Amst). 2015 Aug;32:17-23. doi: 10.1016/j.dnarep.2015.04.009. Epub 2015 May 1.
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.
Mec1（人类中的ATR）是负责酿酒酵母中应对复制应激和DNA损伤时检查点激活的主要激酶。检查点启动需要特定激活剂刺激Mec1激酶活性。酵母中检查点启动的复杂性随着细胞周期不同阶段染色体状态的复杂性而增加。在G1期，检查点钳夹9-1-1对于Mec1激酶的完全激活既是必要的也是充分的，而在G2/M期，强大的检查点功能需要9-1-1和复制体组装蛋白Dpb11（人类TopBP1）。第三种激活剂Dna2在S期专门用于刺激Mec1激酶并启动复制检查点。Dna2是一种必需的核酸酶-解旋酶，对于冈崎片段的正常成熟、双链断裂修复以及保护停滞的复制叉是必需的。值得注意的是，所有三种Mec1激活剂都使用蛋白质的一个无结构区域，该区域包含两个至关重要的芳香族残基，以便激活Mec1。本文讨论了这些检查点激活剂在将异常复制结构引导到检查点复合物中的作用。
