Contact
Biography
- BA, Genetics, University of Cambridge (1989)
- PhD, Cell and Molecular Biology, University of Edinburgh (1994)
- Research Assistant, University of Edinburgh (1994-1995)
- Visiting Postdoctoral Fellow, National Cancer Institute, NIH, USA (1995-2001)
- Wellcome Trust Postdoctoral Fellow, University of Nottingham (2001-2002)
- Royal Society University Research Fellow (2002-2007, renewed 2007-2010)
- Lecturer, University of Nottingham (2010-2014)
- Associate Professor, University of Nottingham (2014-2018)
- Professor, University of Nottingham (2018-present)
Expertise Summary
https://orcid.org/0000-0002-7308-3332
Teaching Summary
I teach a 3rd year module 'Ageing, Sex and DNA Repair' (LIFE3002) in the spring semester. In this module, I examine how the process of ageing is related to DNA damage, study the cellular mechanisms… read more
Research Summary
We are using genetics and biochemistry to understand how DNA replication, recombination and repair operate in the Archaea.
Archaea are the third domain of life alongside bacteria and eukaryotes. Archaea live in extremely harsh environments such as boiling acid pools or salt lakes, which pose enormous challenges for growth and DNA stability. For more information on Archaea, see https://youtu.be/hw-ij3822DY
Salt works at Red Sea, Israel, and acid pool in Yellowstone National Park, USA
We are interested in how DNA replication, recombination and repair have evolved to meet these challenges, and how they operate in an evolutionary lineage that is fundamentally distinct from bacteria and eukaryotes.
The tree of life has three domains
Archaea show many similarities to eukaryotic cells, particularly in the proteins used for DNA replication, repair and recombination. Studies of the archaea may therefore help with the dissection of more complex eukaryotic systems.
We have developed genetic and biochemical systems using Haloferax volcanii as a model organism. Haloferax volcanii was isolated from the Dead Sea and is an obligate halophile.
Haloferax volcanii was isolated from the Dead Sea. It is easily grown in the lab
Haloferax volcanii grows aerobically at 45°C in media containing 2.5 M NaCl, it can be cultivated in the laboratory with ease. Many genetic and biochemical tools are available for Haloferax volcanii.
Sampling for Haloferax volcanii from the Dead Sea
Genetic and biochemical tools for Haloferax volcanii include a markerless gene knockout system, several auxotrophic and antibiotic-resistance markers, reporter genes, an inducible promoter and plasmid vectors for protein over-expression.
Genetic and biochemical tools for Haloferax volcanii
Our research is focused on four areas: DNA replication origins, homologous recombination, DNA double-strand break repair, and DNA helicases.
DNA replication origins
DNA replication initiates at defined sites on the chromosome called origins. Bacteria, which have small circular chromosomes, have one replication origin. Eukaryotes have large linear chromosomes, therefore they require many replication origins.
DNA replication initiates at origins
Archaea have small circular chromosomes like bacteria, but have several replication origins like eukaryotes. The DNA replication machinery used in archaea and eukaryotes is strikingly similar.
DNA replication machinery
The chromosome of Haloferax volcanii has several DNA replication origins. We are investigating how DNA replication initiates at these origins and how this process is regulated.
Haloferax volcanii laboratory strain H26 has four replication origins, but none is needed for DNA replication
Intriguingly, Haloferax volcanii does not need DNA replication origins. In fact, a mutant strain lacking all origins grows significantly faster than the wild type. We have discovered that cells without origins use homologous recombination to initiate DNA replication.
Cells without origins grow faster than wild-type, but the (tryptophan-inducible) radA gene is essential
Homologous recombination
Homologous recombination is an important pathway of DNA repair, it is also used to restart stalled DNA replication and to generate genetic diversity. Homologous recombination involves the exchange of DNA strands of identical sequence.
Strand exchange is catalysed by RadA, which polymerises on DNA
Recombination is carried out by RecA-family recombinases, which catalyse the strand exchange of homologous DNA sequences. Archaeal and eukaryotic recombinases are very similar to each other. We are investigating how recombination in archaea is carried out by RadA.
RecA-family recombinases from archaea, bacteria and eukaryotes
In archaea such as Haloferax volcanii, homologous recombination is carried out with assistance by RadB protein. RadB is related to RadA and the two proteins interact with each other. But unlike RadA, RadB cannot carry out strand exchange. We are investigating the role of RadB.
RadB is related to RadA but cannot catalyse strand exchange
DNA double-strand break repair
Double-stranded breaks in DNA are very dangerous and can lead to cell death or cancer. This type of DNA damage is detected by the Mre11-Rad50 complex, it binds directly to the broken end and helps to coordinate DNA repair.
Mre11-Rad50 complex binds to DNA double strand breaks
We are investigating how the repair of DNA double-strand breaks is carried out in archaea. Intriguingly, deletion of the mre11 or rad50 genes makes Haloferax volcanii more resistant to DNA damage, but the cells recover more slowly.
Cells after irradiation with UV light
After DNA damage, the chromosome of Haloferax volcanii is reorganized into a compacted shape. This process is catalysed by the Mre11-Rad50 complex and may help with the rapid recovery from DNA double-strand breaks.
Chromosomal DNA is compacted after DNA damage
DNA helicases
Helicases are enzymes that separate the two complementary strands of an DNA or RNA duplex. Helicases play many important roles in the cell during processes such as transcription, DNA replication and repair. Mutations in helicase genes are frequently associated with cancer.
Helicases such as Hel308 unwind DNA
Hel308 is a helicase that is conserved across metazoans (multicellular animals) and archaea, but is absent from bacteria and fungi. Hel308 helicase is involved in DNA repair and recombination. We are investigating the role of Hel308 in Haloferax volcanii.
Current lab members Rebecca Lever, Patricia Perez Arnaiz, Laura Mitchell,Thorsten Allers, Victoria Smith, Ambika Dattani, Nathan Jones and Çağla Tosun
Former lab members
2017 Hannah Marriott, Nathan Jones, Patricia Perez Arnaiz, Alexandra Schindl, Laura Mitchell,Thorsten Allers, Jaime Hughes, Rebecca Lever, RisatHaque and Dasha Ausiannikava
2015 Dasha Ausiannikava, Hannah Marriott, Laura Mitchell, Rebecca Gamble-Milner, Charlie Wickham-Smith, Thorsten Allers and Leonardo Oliveira
2013 Rebecca Milner, Thorsten Allers and Kayleigh Wardell
2008 Zhenhong (Belinda) Duan, Michelle Hawkins, Stéphane Delmas, Thorsten Allers, Amy Stroud and Sam Haldenby