DNA replication and genome stability


Group lead: Dr Eva Petermann

Group overview

DNA replication is the process by which dividing cells copy their genetic information. Replication is very important but also dangerous for cells, because if obstacles inhibit the movement of the replication apparatus, this can lead to DNA damage, mutations or cell death. This is called replication stress. My group investigates molecular mechanisms of replication stress in cancer development and treatment.

Our research group

The replication apparatus is also called “replication fork” because of its structure (see Figure, right). Replication forks that encounter obstacles can stall and collapse into DNA double-strand breaks (DSBs), a highly mutagenic and toxic form of DNA damage (Jones and Petermann, 2012; Petermann and Helleday, 2010). This replication fork stalling followed by conversion into DNA damage makes up replication stress.

Endogenous replication stress may be an important driving factor of tumour development. Consequently, cellular factors preventing replication stress are often tumour suppressors, while factors promoting replication stress may be oncogenes. Additionally, many DNA-damaging anti-cancer drugs act by slowing or stalling replication forks to kill cancer cells. Our group is interested in understanding how oncogenes and anti-cancer treatments cause replication stress and how cells respond to this.

We use mammalian cell models and the DNA fibre method, which employs labelling of live cells with nucleoside analogues, which can then be detected by immunofluorescence after DNA fibres have been isolated. This allows us to measure the speed of replication fork progression and whether replication forks stall or restart. Using this approach, we have shown how the oncogenes Cyclin E and Ras cause replication stress (Jones et al, 2013; Kotsantis et al, 2016) and how homologous recombination and transcription modulate the therapeutic action of cancer drugs (Jones et al, 2014, Bowry et al, 2018).  

 Lab page picture for research group description1

Left: Increased RNA synthesis (EU, red) in the nuclei of cells expressing oncogene HRASV12. Middle: Pulse-labelling with thymidine analogues CldU and IdU allows visualising replication fork movement on isolated DNA fibres. HRASV12 slows replication fork progression. Right: DNA damage markers in cells expressing HRASV12. 

Current projects

Transcription-replication conflicts in cancer

Replication stress, or replication-associated DNA damage, occurs frequently in cancer. There is a growing interest in targeting oncogene-induced replication stress for cancer therapy. Effective targeting will require mechanistic understanding of how oncogenes induce replication stress. It is widely appreciated that oncogenes can promote replication stress by de-regulating the cell cycle machinery to increase proliferation. However to promote proliferation, oncogenes also need to hyper-activate the basal transcription machinery. We use DNA fibre approaches to identify new mechanisms of oncogene-induced replication stress (Jones et al., 2013). 

We have evidence for transcription hyper-activation as an alternative and important replication stress mechanism. We recently reported that H-RasV12 induces replication-transcription conflicts, not by de-regulating the cell cycle, but by increasing expression of a general transcription factor (TBP) and global RNA synthesis (Kotsantis et al., 2016). We showed that TBP overexpression can promote replication stress independently of oncogenes.  We are further investigating the mechanisms of oncogene-induced transcription-replication conflicts. We are also investigating transcription-replication conflicts induced by a new class of cancer drugs called BET inhibitors (Bowry et al., 2018). 

Homologous recombination at stalled replication forks

Homologous recombination (HR) is a remarkable genome maintenance pathway that brings together DNA replication and DNA repair. Because of this, it is absolutely central to diseases characterized by replication stress or treated with replication stress-inducing agents. 

It is increasingly evident that HR processes frequently occur at perturbed replication forks, where HR performs novel roles that are distinct from its classic function in DNA double-strand break repair. New insights into the roles of HR at stressed replication forks are relevant for cancer development and therapy. We are particularly interested in understanding how HR can slow and stall forks. 

We use DNA fibre approaches to identify new roles for HR and the central HR factor RAD51 at stalled replication forks. We study how RAD51 modulates fork progression in response to classic chemotherapy, targeted cancer therapies, and environmental mutagens (Jones et al, 2014; Ronson et al., 2018) 

Recent publications

Bowry A, Piberger AL, Rojas P, Saponaro M, Petermann E (2018) BET inhibition induces HEXIM1- and RAD51-dependent conflicts between transcription and replication. Cell Reports 25:2061–2069 

Ronson GE, Piberger AL, Higgs MR, Olsen AL, Stewart GS, McHugh PJ, Petermann E, Lakin ND (2018) PARP1 and PARP2 stabilise replication forks at base excision repair intermediates through Fbh1-dependent Rad51 regulation. Nature Communications 9: 746 

Kotsantis P, Marques Silva L, Irmscher S, Jones RM, Folkes L, Gromak N, Petermann E (2016) Increased global transcription activity as a mechanism of replication stress in cancer. Nature Communications 7:13087 

Kotsantis P, Jones RM, Higgs MR, Petermann E (2015) Cancer therapy and replication stress: forks on the road to perdition. Adv Clin Chem 69:91-138 

Jones RM, Kotsantis P, Stewart GS, Groth P, Petermann E (2014) BRCA2 and RAD51 promote double-strand break formation and cell death in response to Gemcitabine. Mol Cancer Ther 13:2412-2421  

Jones RM, Mortusewicz O, Afzal I, Lorvellec M, Garcia P, Helleday T, Petermann E (2013) Increased replication initiation and conflicts with transcription underlie Cyclin E-induced replication stress. Oncogene 32:3744-3753 

Jones RM, Petermann E (2012) Replication fork dynamics and the DNA damage response. Biochem J 443:13-26 


Group Members

Dr Ann Liza Piberger 

PhD students
Akhil Bowry