AR phosphorylation and CHK2 kinase activity regulates IR-stabilized AR-CHK2 interaction and prostate cancer survival.

Huy Q Ta,Devin G Roller,Melissa L Ivey,Daniel Gioeli,Natalia Dworak

doi:10.7554/elife.51378

Abstract

We have previously demonstrated that checkpoint kinase 2 (CHK2) is a critical negative regulator of androgen receptor (AR) transcriptional activity, prostate cancer (PCa) cell growth, and androgen sensitivity. We have now uncovered that the AR directly interacts with CHK2 and ionizing radiation (IR) increases this interaction. This IR-induced increase in AR-CHK2 interactions requires AR phosphorylation and CHK2 kinase activity. PCa associated CHK2 mutants with impaired kinase activity reduced IR-induced AR-CHK2 interactions. The destabilization of AR - CHK2 interactions induced by CHK2 variants impairs CHK2 negative regulation of cell growth. CHK2 depletion increases transcription of DNAPK and RAD54, increases clonogenic survival, and increases resolution of DNA double strand breaks. The data support a model where CHK2 sequesters the AR through direct binding decreasing AR transcription and suppressing PCa cell growth. CHK2 mutation or loss of expression thereby leads to increased AR transcriptional activity and survival in response to DNA damage.

Highlights

Mammalian cells are continuously being bombarded by endogenous and exogenous forces that jeopardize the integrity of DNA
checkpoint kinase 2 (CHK2) consists of an amino-terminal starting quantities (SQ)/TQ cluster domain (SCD) where threonine 68 serves as a substrate for phosphorylation by ataxia-telangectasia mutated (ATM) kinase Kim et al, 1999; a carboxy-terminal kinase domain (KD) and nuclear localization sequence Ahn et al, 2004; and a central forkhead-associated domain (FHA) that provides an interface for interactions with phosphorylated proteins (Li et al, 2002)
We previously showed that androgen receptor (AR) co-immunoprecipitated with CHK2 immune complexes in several prostate cancer cell lines (Ta et al, 2015)

Summary

Introduction

CHK2 is a serine/threonine protein kinase that plays a crucial role in sensing DNA damage and initiating the DDR, which is comprised of cell cycle arrest, DNA repair, and apoptosis (Matsuoka et al, 1998). There are approximately 24 CHK2 substrates in human cells that have been experimentally validated, including polo-like kinase 1 (PLK1), promyelocytic leukemia protein (PML), E2F1, p53, and cell division cycle 25C (CDC25C) (Garcıa-Limones et al, 2016). These studies show that one mechanism CHK2 utilizes to affect cellular function is through direct protein-protein interactions

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