The Impact of dUTPase on Ribonucleotide Reductase-Induced Genome Instability in Cancer Cells

Chih-Wei Chen,Ning Tsao,Lin-Yi Huang,Yun Yen,Xiyong Liu,Christine Lehman,Yuh-Hwa Wang,Mei-Chun Tseng,Yu-Ju Chen,Yi-Chi Ho,Chian-Feng Chen,Zee-Fen Chang

doi:10.1016/j.celrep.2016.06.094

Abstract

The appropriate supply of dNTPs is critical for cell growth and genome integrity. Here, we investigated the interrelationship between dUTP pyrophosphatase (dUTPase) and ribonucleotide reductase (RNR) in the regulation of genome stability. Our results demonstrate that reducing the expression of dUTPase increases genome stress in cancer. Analysis of clinical samples reveals a significant correlation between the combination of low dUTPase and high R2, a subunit of RNR, and a poor prognosis in colorectal and breast cancer patients. Furthermore, overexpression of R2 in non-tumorigenic cells progressively increases genome stress, promoting transformation. These cells display alterations in replication fork progression, elevated genomic uracil, and breaks at AT-rich common fragile sites. Consistently, overexpression of dUTPase abolishes R2-induced genome instability. Thus, the expression level of dUTPase determines the role of high R2 in driving genome instability in cancer cells.

Highlights

Genome instability in cancers is a driving force for tumor evolution that contributes to the development of distant metastasis or resistance to anti-cancer treatments (Burrell et al, 2013b; Bedard et al, 2013)
We found that the amounts of 53BP1 foci were much higher in MDA-MB231 and LOVO cells compared with MCF7 and HT29 cells (Figure 1A)
The western blot analysis of deoxynucleotide triphosphates (dNTPs) synthesis enzymes showed that MDA-MB231 and LOVO cells shared a common feature in having very low expression of deoxyuridine triphosphate (dUTP) pyrophosphatase (dUTPase) protein (Figure 1C)

Summary

Introduction

Genome instability in cancers is a driving force for tumor evolution that contributes to the development of distant metastasis or resistance to anti-cancer treatments (Burrell et al, 2013b; Bedard et al, 2013). In the past three decades, signaling pathways controlling checkpoints and DNA repair have been extensively studied in cancer development (Kruiswijk et al, 2015; Roos et al, 2016; Jeggo et al, 2016). The fidelity of the incorporation of four deoxynucleotide triphosphates (dNTPs) during DNA replication and repair is the foundation of genome stability (Mathews, 2015), our understanding of how dNTP supply governs genome instability in cancers is relatively limited. Replication stress is one important factor that causes genome instability (Chan et al, 2009, Burrell et al, 2013a, Zeman and Cimprich, 2014, Minocherhomji et al, 2015). How the alteration in dNTP synthesis affects genome instability via replication stress in cancer cells is not clear

Results

Discussion

Conclusion