Ataxia telangiectasia-mutated phosphorylates Chk2 in vivo and in vitro

The protein kinase Chk2, the mammalian homolog of the budding yeast Rad53 and fission yeast Cds1 checkpoint kinases, is phosphorylated and activated in response to DNA damage by ionizing radiation (IR), UV irradiation, and replication blocks by hydroxyurea (HU). Phosphorylation and activation of Chk2 are ataxia telangiectasia-mutated (ATM) dependent in response to IR, whereas Chk2 phosphorylation is ATM-independent when cells are exposed to UV or HU. Here we show that in vitro, ATM phosphorylates the Ser-Gln/Thr-Gln (SQ/TQ) cluster domain (SCD) on Chk2, which contains seven SQ/TQ motifs, and Thr68 is the major in vitro phosphorylation site by ATM. ATM- and Rad3-related also phosphorylates Thr68 in addition to Thr26 and Ser50, which are not phosphorylated to a significant extent by ATM in vitro. In vivo, Thr68 is phosphorylated in an ATM-dependent manner in response to IR, but not in response to UV or HU. Substitution of Thr68 with Ala reduced the extent of phosphorylation and activation of Chk2 in response to IR, and mutation of all seven SQ/TQ motifs blocked all phosphorylation and activation of Chk2 after IR. These results suggest that in vivo, Chk2 is directly phosphorylated by ATM in response to IR and that Chk2 is regulated by phosphorylation of the SCD.     

The impact of multiplex genetic testing on disease risk perceptions

This study assessed the effects of multiplex genetic testing on disease risk perceptions among 216 healthy adults. Participants, aged 25–40, were recruited through the Multiplex Initiative, which offered a genetic susceptibility test for eight common diseases. Participants completed baseline telephone and web‐based surveys prior to making the testing decision. Three months after the receipt of mailed test results, participants completed a follow‐up telephone survey. Risk perceptions for the eight diseases were measured at baseline and follow‐up, along with beliefs about genetic causation of those diseases. The main results were: (i) mean risk perceptions were considerably stable from baseline to follow‐up; (ii) the best predictors of follow‐up risk perceptions were the corresponding baseline perceptions and family history; and (iii) within‐individuals, most participants increased or decreased their risk perceptions for specific diseases in concordance with the number of risk markers they carry, their family history and their beliefs about genetic causality of diseases. In conclusion, participants presented a vigilant approach to the interpretation of genetic test results, which provides reassurance with regard to a potential inflation of risk perceptions in the population because of multiplex genetic testing.