Tumor suppressor Chk2 is a kinase essential for p53 transcriptional and apoptotic activities. Although mutations of p53 is present in more than half of all tumors, mutations of Chk2 in cancers are rare suggesting that Chk2 may be inactivated by unknown alternative mechanisms. Investigated one such alternative mechanism using acute promyelocytic leukemia (APL) as a model. Although p53-inactivating mutations are extremely rare in APL, t(15;17) chromosomal translocation which fuses retinoic acid receptor (RARalpha) to PML (promyelocytic leukemia) is almost always present, while the other PML allele is intact. We find that in normal cells, PML concentrates a subset of Chk2 into PML nuclear bodies and facilitates its autophosphorylation step, an essential step for Chk2 activity that occurs after phosphorylation of Thr68 by the upstream kinase ATM (ataxia telangiectasia mutated). In APL, PML/RARalpha suppresses Chk2 by dominantly inhibiting the autophosphorylation step. Inactivation of PML/RARalpha with all-trans retinoic acid (ATRA) restores Chk2 localization and autophosphorylation. Thus, by fusing PML with RARalpha, the APL cells have converted a Chk2 activator to a dominant suppressor compromising the Chk2-p53 apoptotic pathway. We also discovered that Chk2 is also inactivated when cells are in low energy producing states, like hypoxia or after treatment with 2-deoxyglucose (2-DG), which decreases ATP. Although the upstream ATM kinase activity is not affected under these conditions, phosphorylation of Thr68 and autophosphorylation are decreased after DNA damage in low energy states. Okadaic acid treatment reversed the inhibition of the Chk2 phosphorylation suggesting that a phosphatase mediates the inactivation of Chk2 in low energy states. Furthermore, with hypoxia or 2-DG treatment, PML cannot recruit Chk2 into PML nuclear bodies and PML-Chk2 interaction disappears. The loss of PML-Chk2 interaction in low energy states may explain the inhibition of the autophosphorylation step. Taken together, our results suggest that even without Chk2 mutation, Chk2 activity and Chk2-mediated apoptosis can be indirectly inhibited by PML disruption, which occurs with PML/RARalpha translocation, as well as by low energy environment.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Intramural Research (Z01)
Project #
1Z01HL002243-07
Application #
7157866
Study Section
(MH)
Project Start
Project End
Budget Start
Budget End
Support Year
7
Fiscal Year
2005
Total Cost
Indirect Cost
Name
U.S. National Heart Lung and Blood Inst
Department
Type
DUNS #
City
State
Country
United States
Zip Code
Park, Sung-Jun; Ahmad, Faiyaz; Um, Jee-Hyun et al. (2017) Specific Sirt1 Activator-mediated Improvement in Glucose Homeostasis Requires Sirt1-Independent Activation of AMPK. EBioMedicine 18:128-138
Bitterman, Jacob L; Chung, Jay H (2015) Metabolic effects of resveratrol: addressing the controversies. Cell Mol Life Sci 72:1473-88
Kang, Hyeog; Suh, Jeong-Yong; Jung, Young-Sang et al. (2011) Peptide switch is essential for Sirt1 deacetylase activity. Mol Cell 44:203-13
Yang, Shutong; Liu, Aiyi; Weidenhammer, Adam et al. (2009) The role of mPer2 clock gene in glucocorticoid and feeding rhythms. Endocrinology 150:2153-60
Kang, Hyeog; Jung, Jae-Won; Kim, Myung K et al. (2009) CK2 is the regulator of SIRT1 substrate-binding affinity, deacetylase activity and cellular response to DNA-damage. PLoS One 4:e6611
Lee, Min-Young; Kim, Myoung-Ae; Kim, Hyun-Ju et al. (2007) Alkylating agent methyl methanesulfonate (MMS) induces a wave of global protein hyperacetylation: implications in cancer cell death. Biochem Biophys Res Commun 360:483-9
Kim, Myoung-Ae; Kim, Hyun-Ju; Brown, Alexandra L et al. (2007) Identification of novel substrates for human checkpoint kinase Chk1 and Chk2 through genome-wide screening using a consensus Chk phosphorylation motif. Exp Mol Med 39:205-12
Kang, Sung Gyun; Brown, Alexandra L; Chung, Jay H (2007) Oxygen tension regulates the stability of insulin receptor substrate-1 (IRS-1) through caspase-mediated cleavage. J Biol Chem 282:6090-7
Um, Jee Hyun; Yang, Shutong; Yamazaki, Shin et al. (2007) Activation of 5'-AMP-activated kinase with diabetes drug metformin induces casein kinase Iepsilon (CKIepsilon)-dependent degradation of clock protein mPer2. J Biol Chem 282:20794-8
Zhuang, Jing; Zhang, Junran; Willers, Henning et al. (2006) Checkpoint kinase 2-mediated phosphorylation of BRCA1 regulates the fidelity of nonhomologous end-joining. Cancer Res 66:1401-8

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