SIRT1 and LSD1 competitively regulate KU70 functions in DNA repair and mutation acquisition in cancer cells.

Mendel Roth,Wen Yong Chen,Zhiqiang Wang

doi:10.18632/oncotarget.10328

Mendel Roth, Wen Yong Chen + Show 1 more

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https://doi.org/10.18632/oncotarget.10328

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Journal: Oncotarget	Publication Date: Jun 30, 2016
Citations: 26	License type: cc-by

Affiliation: Beckman Research Institute

Abstract

Acquisition of BCR-ABL mutations underlies drug resistance of chronic myeloid leukemia (CML) to tyrosine kinase inhibitors, but the molecular mechanisms of mutation acquisition are poorly understood. We previously showed that lysine deacetylase sirtuin 1, SIRT1, promotes acquisition of BCR-ABL mutations in association with enhancing KU70 mediated non-homologous end joining DNA repair. In this study, we demonstrate that lysine specific demethylase 1 (LSD1) plays an opposite role to SIRT1 in regulating DNA repair and mutation acquisition. In response to therapeutic stress and DNA damage, LSD1 and SIRT1 compete for binding to KU70 on DNA damage foci globally and on the ABL locus. The recruitment of SIRT1 or LSD1 to KU70 impacts chromatin structure but does not correlate well with their direct histone modification functions, and SIRT1 helps maintain histone H4K16 acetylation and open chromatin for repair. The competitive KU70 binding by these proteins affects cancer cells' ability to repair broken DNA and acquire resistant genetic mutations in CML and prostate cancer cells. We identify that the core domain of KU70 binds both LSD1 and SIRT1, forming a molecular basis for the competition. The C-terminal SAP motif of KU70 mediates LSD1/SIRT1 competitive interaction by suppressing LSD1 binding to KU70 and ectopic expression of SAP-deleted KU70 to CML cells compromises their ability to acquire BCR-ABL mutations. Our study reveals a novel cellular stress response mechanism in cancer cells and a key role of LSD1/SIRT1/KU70 dynamic interaction in regulating DNA repair and mutation acquisition.

Highlights

Transformation of hematopoietic stem cells by the BCR-ABL fusion oncogene leads to development of chronic myeloid leukemia (CML)
Our initial co-immunoprecipitation pilot study indicated that both SIRT1 and lysine specific demethylase 1 (LSD1) interacted with KU70
Opposite KU70 interaction pattern was observed in these cells, i.e. KU70 was bound to SIRT1 in the untreated KU812 (Figure 1B) and K562 (Supplementary Figure S1) cells, but after imatinib mesylate (IM) treatment, KU70 became more associated with LSD1

Summary

Introduction

Transformation of hematopoietic stem cells by the BCR-ABL fusion oncogene leads to development of chronic myeloid leukemia (CML). To dissect the mechanisms of resistance, we previously developed a culture model with a blast crisis CML cell line that recapitulates clinical CML acquired resistance through BCR-ABL mutations [4]. Using this model, we showed that NAD+ dependent protein lysine deacetylase SIRT1 is critically involved in promoting acquisition of BCR-ABL mutations in response to IM treatment [5]. NHEJ repair is initiated when KU70/KU80 heterodimer binds to broken DNA ends Both KU factors are essential for NHEJ as deletion of either one leads to DSB repair impairment and sensitivity to www.impactjournals.com/oncotarget radiation [9, 10]. We have shown that SIRT1 promotes acquisition of resistant BCR-ABL mutations in CML cells in association with its ability to stimulate aberrant NHEJ activity by deacetylating KU70 [5, 6]

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