What is ATM Chk2?
What is ATM Chk2?
DNA damage is a key factor both in the evolution and treatment of cancer. Cellular responses to DNA damage are coordinated primarily by two distinct kinase signaling cascades, the ATM-Chk2 and ATR-Chk1 pathways, which are activated by DNA double-strand breaks (DSBs) and single-stranded DNA respectively.
What does ATM and ATR do?
Depending on the nature of the DNA lesion, both ATM and ATR can induce the G1/S, G2/M and S-phase checkpoints. By doing so, they ensure that the cell accurately repairs the DNA damage before DNA replication or cell division occurs.
What are Chk1 and Chk2?
The checkpoint kinases Chk1 and Chk2 phosphorylate the carboxy-terminal domain of hBRCA2, a protein involved in recombination-mediated DNA repair (HRR) and replication fork maintenance. Cells deficient in hBRCA2 are hypersensitive to DNA damaging agents.
What is the difference between ATR and ATM?
Whereas ATM is primarily activated by double-stranded DNA breaks (DSBs), ATR responds to a broad spectrum of DNA damage, including DSBs and a variety of DNA lesions that interfere with replication.
How is ATM activated?
ATM exists in an inactive state in resting cells but can be activated by the Mre11-Rad50-Nbs1 (MRN) complex and other factors at sites of DNA breaks. In addition, oxidation of ATM activates the kinase independently of the MRN complex.
How is ATR activated?
The activation of the ATR-Chk1 pathway is triggered by RPA-coated single-stranded DNA (ssDNA), a nucleoprotein structure commonly generated at sites of DNA damage and stressed replication forks (1, 2). Together, these proteins enable TopBP1 to stimulate the kinase activity of ATR–ATRIP.
What is ATM in DNA repair?
Ataxia telangiectasia mutated (ATM), a core component of the DNA repair system, is activated to enhance the homologous recombination (HR) repair pathway upon DNA double-strand breaks.
What is the role of ATR?
In mammalian cells, two important regulators of DNA damage checkpoints are ATR and ATM, unconventional protein kinases that phosphorylate and activate signal transduction pathways that ultimately interface with the Cdk/Cyclin machinery.
Is Chk1 a tumor suppressor?
Further, emerging evidence suggests that Chk1 does not appear to be a tumor suppressor; instead, it promotes tumor growth and may contribute to anticancer therapy resistance.
How do Chk1 inhibitors work?
By inhibiting Chk1, cancer cells lose the ability to repair damaged DNA which allows chemotherapeutic agents to work more effectively. Combining DNA damaging therapies such as chemotherapy or radiation treatment with Chk1 inhibition enhances targeted cell death and provides synthetic lethality.
Is ATM phosphorylated?
In the delayed response ATM phosphorylates the inhibitor of p53, MDM2, and p53, which is also phosphorylated by Chk2. The resulting activation and stabilization of p53 leads to an increased expression of Cdk inhibitor p21, which further helps to keep Cdk activity low and to maintain long-term cell cycle arrest.
What is the ATM gene responsible for?
The ATM gene provides instructions for making a protein that is located primarily in the nucleus of cells, where it helps control the rate at which cells grow and divide.
How are ATM CHK2 and ATR CHk1 inhibitors work?
Inactivation of the ATM-CHK2 and ATR-CHK1 pathways efficiently sensitizes malignant cells to radiotherapy and chemotherapy. Moreover, ATR and CHK1 inhibitors selectively kill tumor cells that present high levels of replication stress, have a deficiency in p53 (or other DDR players), or upregulate the ATR-CHK1 module.
Which is part of the atm-chk2 Cascade?
The ataxia telangiectasia mutated serine/threonine kinase (ATM)/checkpoint kinase 2 (CHEK2, best known as CHK2) and the ATM and Rad3-related serine/threonine kinase (ATR)/CHEK1 (best known as CHK1) cascades are the 2 major signaling pathways driving the DNA damage response (DDR), a network of proces …
Is the ATR-Chk1 pathway upregulated in neoplasms?
In contrast, the ATR-CHK1 pathway is often upregulated in neoplasms and is believed to promote tumor growth, although some evidence indicates that ATR and CHK1 may also behave as haploinsufficient oncosuppressors, at least in a specific genetic background.