Figure 1. Treatment of HeLa cells with UV stimulates phosphorylation of Chk2 at Thr68, detected by the PathScan® Phospho-Chk2 (Thr68) Sandwich ELISA Kit #7037, but does not affect the levels of total Chk2 detected by PathScan® Total Chk2 Sandwich ELISA Kit #7045. HeLa cells (80-90% confluent) were treated with 100 mJ/cm2 UV with 1 hour recovery at 37ºC. The absorbance readings at 450 nm are shown in the top figure, while the corresponding western blots using Chk2 (1C12) Mouse mAb #3440 (left panel) or Phospho-Chk2 (Thr68) (C13C1) RmAb #2197 (right panel) are shown in the bottom figure.
Figure 2. The relationship between the protein concentration of lysates from untreated and UV-treated HeLa cells and the absorbance at 450 nm using the PathScan® Total Chk2 Sandwich ELISA Kit #7045 is shown.
The PathScan® Total Chk2 Sandwich ELISA Kit is a solid phase sandwich enzyme-linked immunosorbent assay (ELISA) that detects endogenous levels of Chk2. A Chk2 rabbit antibody has been coated onto the microwells. After incubation with cell lysates, Chk2 (phospho and nonphospho) is captured by the coated antibody. Following extensive washing, a Chk2 mouse detection antibody is added to the captured phospho and nonphospho Chk2 protein. Anti-mouse IgG, HRP-linked Antibody #7076 is then used to recognize the bound detection antibody. HRP substrate, TMB, is added to develop color. The magnitude of the absorbance for this developed color is proportional to the quantity of total Chk2.
Antibodies in kit are custom formulations specific to kit.
CST's PathScan® Chk2 Sandwich ELISA Kit #7045 detects endogenous levels of total Chk2 protein (see Figure 1). The kit sensitivity is shown in Figure 2. This kit detects proteins from the indicated species, as determined through in-house testing, but may also detect homologous proteins from other species.
Chk2 is the mammalian orthologue of the budding yeast Rad53 and fission yeast Cds1 checkpoint kinases (1-3). The amino-terminal domain of Chk2 contains a series of seven serine or threonine residues (Ser19, Thr26, Ser28, Ser33, Ser35, Ser50, and Thr68) each followed by glutamine (SQ or TQ motif). These are known to be preferred sites for phosphorylation by ATM/ATR kinases (4,5). After DNA damage by ionizing radiation (IR), UV irradiation, or hydroxyurea treatment, Thr68 and other sites in this region become phosphorylated by ATM/ATR (5-7). The SQ/TQ cluster domain, therefore, seems to have a regulatory function. Phosphorylation at Thr68 is a prerequisite for the subsequent activation step, which is attributable to autophosphorylation of Chk2 at residues Thr383 and Thr387 in the activation loop of the kinase domain (8).
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PathScan is a trademark of Cell Signaling Technology, Inc.