My research aims to understand how DNA is replicated in mammalian cells. Each cell division requires the precise copying of the genome, failure to regulate this process leads to mutation and chromosome abnormalities that are associated with cancer.
The key research aims are to better understand the replication licensing and initiation process of DNA replication. Use of cell-based and cell-free DNA replication techniques provide powerful tools to monitor key regulatory steps in this process. The long term goal is to identify differences between regulation of DNA replication in cancerous cells and normal tissues, to identify new therapeutic targets.
I would be happy to hear from prospective students at MSc by Research level or PhD level to discuss projects on mammalian DNA replication, DNA replication stress and cancer biology.
All living organisms have evolved highly conserved mechanisms to maintain genomic stability. DNA replication in mammalian cells occurs at thousands of replication origins that are activated only one once per cell cycle to ensure precise duplication of the genome. A seies of highly orchestrated events that occur to maintain fidelity during DNA replication and many of these events are regulated by the activity of cyclin dependent kinases (CDKs). Precise control of the cell cycle is essential to maintain a healthy genome. Mutations that arise in genes that regulate the cell cycle can lead to a loss of control for cellular proliferation and cancer. Understanding these fundamental processes will enable identification of new therapeutic targets in cancer.
My research is focused on the transition from G1 phase to S-phase. Particularly the regulatory events that control the initiation phase of DNA replication, where the replication bubble forms and DNA polymerases begin to copy the chromosome. To study this process I use a reconstituted cell free system that utilised a synchronised population of G1 nuclei that can be induced to initiate DNA replication by addition of recombinant cyclin A-CDK2 or S-phase cytosolic extracts. This method enables fine dissection of the initiation process and can facilitate functional characterisation of replication proteins. Using this and other techniques research in my lab currently focuses in 3 areas:
(i) Regulation of cell cycle progression by Ciz1.
Ciz1 promotes DNA replication by cooperating with cyclin A-CDK2 to promote initiation of DNA replication. The role of Ciz1 in cellular proliferation is beginning to emerge with recent studies showing that Ciz1 has both tumour suppressor functions and oncogenic functions. The oncogenic properties are beginning to be identified and likely related to the ability of Ciz1 to enhance CDK activity. Ciz1 is frequently over-expressed in cancer cell lines and tumours and cancer specific splice variants can be detected in patients’ serum at an early stage of small cell lung carcinoma and non small cell lung carcinoma. Importantly, cancer specific splice variants can be targeted by RNA interference to restrict tumour growth in mouse models, suggesting that Ciz1 may be a useful therapeutic target. Research in my lab continues to refine the regulatory role of Ciz1 in DNA replication.
(ii) Regulation of initiation of DNA replication by cyclin A-CDK2
The cell cycle is regulated by the sequential activities of cyclin-CDK complexes. Using contact inhibition and serum starvation cell cycle synchronisation can be used to produce cell cycle stage specific nuclei and extracts. Using a combination of G1 nuclei, G1 cytosolic extracts and recombinant cyclin A it is possible to initiate DNA replication. Using this method the precise steps that regulate this process can be investigated. The aim here is to monitor replication protein assembly during the transition from G1 into S-phase after addition of cyclin A-CDK2. This will enable molecular dissection of events in late G1 prior to S-phase entry in mammalian cells.
(iii) Role of Ap4A in regulation of initiation of DNA replication in response to DNA damage.
Cells have developed extremely sensitive mechanisms to detect and repair genetic damage as mutations arise. There are multiple systems that mediate signalling cascades to inhibit DNA replication, this enables the cells to repair DNA damage and restricts propagation of mutations to daughter cells. During DNA damage a small ‘alarmone’ diadenosdine tetraphosphate (Ap4A) is produced and research in my lab aims to determine the role of Ap4A in DNA replication after DNA damage and repair.
Research in my lab is funded by NWCR.
Currently I teach the following modules:-
- BIOL112 Cell structure and function: introduction to cell cycle regulation and how mutations in cell cycle regulation can lead to cancer.
- BIOL115 Protein biochemistry: Michaelis-Menten kinetics of simple biological systems, drug metabolism and modes of inhibition. I also provide 2 practical classes:Chromatography and enzyme kinetic.
- BIOL303 Cell cycle and stem cells: Detailed molecular mechanisms for cell cycle progression and how these pathways are adapted for maintenance of stem cell populations.
- BIOL386/Biol387 Bioscience Laboratory Project: Undergraduate research projects in cancer biology and cell cycle regulation
- BIOL390 Bioscience Literature Review: Literature reviews in molecular mechanisms of cancer and cell cycle regulation by cyclin dependent kinases.
- BIOL437 Molecular basis of cancer: This module covers molecular aspects of cancer biology. Teaching includes molecular targetting of oncogenes, angiogenesis, replicative immortality (telomerase and ALT), biomarkers and stratification of disease.
- BIOL466 Bioscience Laboratory Project: Postgraduate research projects in cancer biology and cell cycle regulation.
