Stress light-induced formation

Fig. 8 Stress-Fiber (SF) formation in triangular (left panel), square (central panel) and hexagonal (right panel) shaped cells. Subplots (a), (d) and (g) correspond to the cells at the time of adhesion and hence they do not have any SF. Once the cells are strongly adhered to the substrate, cytoskeletal contractile force induce SF formation which are shown in subplots (b), (e) and (h) by dark, thick lines. Thickness and darkness of the lines are proportional to the density of SF. Less tensile and compressed regions are thinner and shaded lightly.

Members of the phosphoinositide (PI)-3 kinase family appear to be involved in the phosphorylation of H2A.X. The SQ motif matches a common target site for these kinases and the formation of y-H2A.X in response to double stranded breaks is inhibited by wortmannin, an inhibitor of PI-3 kinases [63]. Examination of cell lines deficient in the PI-3 kinase ATM indicated that it has a major role in phosphorylating H2A.X in response to double strand breaks [64]. ATM can phosphorylate H2A.X in vitro suggesting that it may directly phosphorylate H2A.X in vivo [64]. Another PI-3 kinase ATR appears to be involved in phosphorylating H2A.X in response to replicational stress induced by treatment of dividing cells with hydroxyurea or by irradiating them with ultraviolet light [65]. It has been hypothesized that PI-3 kinases such as ATM are recruited to, or activated at, the site of the double stranded break and then phosphorylate H2A.X molecules around the break point [40,64,66]. 

The underlying concepts of the model, based on interfacial stress between Si and its anodic oxide, are briefly reviewed at its core is the dynamic competition between oxide formation (cf. Equation 2.52) and dissolution in dilute (0.1-0.2 M) NH4F solutions with pH of about 4. The processes of light- or potential-induced oxidation and etching in HF and HF2" occur simultaneously and the overall reactions are as follows ... 

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