Homeodomain-interacting protein kinase 2 regulates DNA damage response through interacting with heterochromatin protein 1γ

The tumour suppressor p53 is activated to induce cell-cycle arrest or apoptosis in the DNA damage response (DDR). p53 phosphorylation at Ser46 by HIPK2 (homeodomain-interacting protein kinase 2) is a critical event in apoptosis induction. Interestingly, HIPK2 is degraded by Mdm2 (a negative regulator of p53), whereas Mdm2 is downregulated by HIPK2 through several mechanisms. Here, we develop a four-module network model for the p53 pathway to clarify the role of interplay between Mdm2 and HIPK2 in the DDR evoked by ultraviolet radiation. By numerical simulations, we reveal that Mdm2-dependent HIPK2 degradation promotes cell survival after mild DNA damage and that inhibition of HIPK2 degradation is sufficient to trigger apoptosis. In response to severe damage, p53 phosphorylation at Ser46 is promoted by the accumulation of HIPK2 due to downregulation of nuclear Mdm2 in the later phase of the response. Meanwhile, the concentration of p53 switches from moderate to high levels, contributing to apoptosis induction. We show that the presence of three mechanisms for Mdm2 downregulation, i.e. repression of mdm2 expression, inhibition of its nuclear entry and HIPK2-induced degradation, guarantees the apoptosis of irreparably damaged cells. Our results agree well with multiple experimental observations, and testable predictions are also made. This work advances our understanding of the regulation of p53 activity in the DDR and suggests that HIPK2 should be a significant target for cancer therapy.

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High Fidelity Deep Sequencing Reveals No Effect of ATM, ATR, and DNA-PK Cellular DNA Damage Response Pathways on Adenovirus Mutation Rate

Viruses ◽

10.3390/v11100938 ◽

2019 ◽

Vol 11 (10) ◽

pp. 938 ◽

Cited By ~ 1

Author(s):

Risso-Ballester ◽

Sanjuán

Keyword(s):

Dna Damage ◽

Protein Kinase ◽

Dna Damage Response ◽

Deep Sequencing ◽

Molecular Mechanisms ◽

Spontaneous Mutation ◽

High Fidelity ◽

Dna Viruses ◽

Damage Response ◽

Cellular Dna

Most DNA viruses exhibit relatively low rates of spontaneous mutation. However, the molecular mechanisms underlying DNA virus genetic stability remain unclear. In principle, mutation rates should not depend solely on polymerase fidelity, but also on factors such as DNA damage and repair efficiency. Most eukaryotic DNA viruses interact with the cellular DNA damage response (DDR), but the role of DDR pathways in preventing mutations in the virus has not been tested empirically. To address this goal, we serially transferred human adenovirus type 5 in cells in which the telangiectasia-mutated PI3K-related protein kinase (ATM), the ATM/Rad3-related (ATR) kinase, and the DNA-dependent protein kinase (DNA-PK) were chemically inactivated, as well as in control cells displaying normal DDR pathway functioning. High-fidelity deep sequencing of these viral populations revealed mutation frequencies in the order of one-millionth, with no detectable effect of the inactivation of DDR mediators ATM, ATR, and DNA-PK on adenovirus sequence variability. This suggests that these DDR pathways do not play a major role in determining adenovirus genetic diversity.

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ATF4-Mediated Upregulation of REDD1 and Sestrin2 Suppresses mTORC1 Activity during Prolonged Leucine Deprivation

Journal of Nutrition ◽

10.1093/jn/nxz309 ◽

2019 ◽

Vol 150 (5) ◽

pp. 1022-1030 ◽

Cited By ~ 5

Author(s):

Dandan Xu ◽

Weiwei Dai ◽

Lydia Kutzler ◽

Holly A Lacko ◽

Leonard S Jefferson ◽

...

Keyword(s):

Amino Acids ◽

Dna Damage ◽

Amino Acid ◽

Protein Kinase ◽

Dna Damage Response ◽

Dependent Manner ◽

Mouse Embryo Fibroblasts ◽

Damage Response ◽

Mtorc1 Activation ◽

In Cells

ABSTRACT Background The protein kinase target of rapamycin (mTOR) in complex 1 (mTORC1) is activated by amino acids and in turn upregulates anabolic processes. Under nutrient-deficient conditions, e.g., amino acid insufficiency, mTORC1 activity is suppressed and autophagy is activated. Intralysosomal amino acids generated by autophagy reactivate mTORC1. However, sustained mTORC1 activation during periods of nutrient insufficiency would likely be detrimental to cellular homeostasis. Thus, mechanisms must exist to prevent amino acids released by autophagy from reactivating the kinase. Objective The objective of the present study was to test whether mTORC1 activity is inhibited during prolonged leucine deprivation through ATF4-dependent upregulation of the mTORC1 suppressors regulated in development and DNA damage response 1 (REDD1) and Sestrin2. Methods Mice (8 wk old; C57Bl/6 × 129SvEV) were food deprived (FD) overnight and one-half were refed the next morning. Mouse embryo fibroblasts (MEFs) deficient in ATF4, REDD1, and/or Sestrin2 were deprived of leucine for 0–16 h. mTORC1 activity and ATF4, REDD1, and Sestrin2 expression were assessed in liver and cell lysates. Results Refeeding FD mice resulted in activation of mTORC1 in association with suppressed expression of both REDD1 and Sestrin2 in the liver. In cells in culture, mTORC1 exhibited a triphasic response to leucine deprivation, with an initial suppression followed by a transient reactivation from 2 to 4 h and a subsequent resuppression after 8 h. Resuppression occurred concomitantly with upregulated expression of ATF4, REDD1, and Sestrin2. However, in cells lacking ATF4, neither REDD1 nor Sestrin2 expression was upregulated by leucine deprivation, and resuppression of mTORC1 was absent. Moreover, in cells lacking either REDD1 or Sestrin2, mTORC1 resuppression was attenuated, and in cells lacking both proteins resuppression was further blunted. Conclusions The results suggest that leucine deprivation upregulates expression of both REDD1 and Sestrin2 in an ATF4-dependent manner, and that upregulated expression of both proteins is involved in resuppression of mTORC1 during prolonged leucine deprivation.

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DNA-PKcs-interacting protein KIP binding to TRF2 is required for the maintenance of functional telomeres

Biochemical Journal ◽

10.1042/bj20131395 ◽

2014 ◽

Vol 463 (1) ◽

pp. 19-30 ◽

Cited By ~ 9

Author(s):

Prabhat Khadka ◽

Ji Hoon Lee ◽

Seung Han Baek ◽

Sue Young Oh ◽

In Kwon Chung

Keyword(s):

Dna Damage ◽

Dna Damage Response ◽

Binding Activity ◽

Interacting Protein ◽

Damage Response

DNA-PKcs-interacting protein KIP interacts with TRF2 and enhances the telomere binding activity of TRF2. Depletion of KIP induces telomere-damage response foci. Thus KIP plays important roles in the maintenance of functional telomeres and the regulation of telomere-associated DNA-damage response.

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