People

White, Prof Malcolm: [Group PI] Professor

tel: 01334 463432
fax:
room: 307 Annexe
email: mfw2@st-andrews.ac.uk

Defending the genome

DNA Repair

All organisms invest considerable resources in the maintenance, protection and repair of their genetic material, DNA. This is unsurprising, as the consequences of DNA damage can be mutation, cell death and, in humans, cancer. We utilise a variety of interdisciplinary techniques ranging from microbiology and genetics through biochemistry and molecular biology to biophysics and structural biology to study DNA repair proteins and pathways in archaea and humans.

CRISPR

Cells must also defend their genomes against attack by selfish genetic elements such as viruses. Although CRISPR is widely known as a genome editing technology, the CRISPR system functions as an adaptive immune system in prokaryotes. CRISPR is not synonymous with Cas9, which is an unusual type II system that is rarely present in bacteria. In contrast, type I and type III systems are much more common, and arguably much more interesting. Our lab studies type III CRISPR systems, which confer a complex, multi-layered defence against mobile genetic elements. Detection of viral RNA leads the Cas10 subunit of type III systems to generate the second messenger cyclic oligoadenylate (cOA), which sculpts the cellular response to infection. cOA activates a range of effector proteins, including the ribonuclease Csm6/Csx1, which degrades RNA non-specifically to slow down both viral and host metabolism and “buy some time”. We recently identified and characterised a “Ring nuclease” enzyme, which degrades the cOA signal and returns cells to an uninfected state following viral RNA clearance. Predictably, viruses have evolved countermeasures known as anti-CRISPRs, and we recently discovered a viral anti-CRISPR that circumvents type III CRISPR immunity by rapidly degrades the cOA signalling molecule.source: research@st-andrews[source: research@st-andrews]

Defending the genome

DNA Repair

All organisms invest considerable resources in the maintenance, protection and repair of their genetic material, DNA. This is unsurprising, as the consequences of DNA damage can be mutation, cell death and, in humans, cancer. We utilise a variety of interdisciplinary techniques ranging from microbiology and genetics through biochemistry and molecular biology to biophysics and structural biology to study DNA repair proteins and pathways in archaea and humans.

CRISPR

Cells must also defend their genomes against attack by selfish genetic elements such as viruses. Although CRISPR is widely known as a genome editing technology, the CRISPR system functions as an adaptive immune system in prokaryotes. CRISPR is not synonymous with Cas9, which is an unusual type II system that is rarely present in bacteria. In contrast, type I and type III systems are much more common, and arguably much more interesting. Our lab studies type III CRISPR systems, which confer a complex, multi-layered defence against mobile genetic elements. Detection of viral RNA leads the Cas10 subunit of type III systems to generate the second messenger cyclic oligoadenylate (cOA), which sculpts the cellular response to infection. cOA activates a range of effector proteins, including the ribonuclease Csm6/Csx1, which degrades RNA non-specifically to slow down both viral and host metabolism and “buy some time”. We recently identified and characterised a “Ring nuclease” enzyme, which degrades the cOA signal and returns cells to an uninfected state following viral RNA clearance. Predictably, viruses have evolved countermeasures known as anti-CRISPRs, and we recently discovered a viral anti-CRISPR that circumvents type III CRISPR immunity by rapidly degrades the cOA signalling molecule.[source: Symbiosis]

Prof Malcolm White
Biomolecular Sciences Building
University of St Andrews
North Haugh
St Andrews
KY16 9ST
Fife
UK

Related Content:

research@st-andrews
Structural Biology
School of Biology
Biomedical Sciences Research Complex
Biomedical Sciences Research Complex

Symbiosis Profile Page
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Athukoralage, Mr Januka: Postgraduate Student/Demonstrator

tel:
fax:
room:
email: jsa8@st-andrews.ac.uk

[source: research@st-andrews]

My research is focused on virus-host conflict in bacteria and archaeaAlmost all prokaryotes use an adaptive immune system known as CRISPR-Cas to defend against infection by viruses and phage. Guided by genetic memories of past infection, CRISPR-Cas systems detect and degrade foreign genetic material. We study the type III CRISPR-Cas system which also synthesises cyclic oligoadenylate second messengers in response to infection. Cyclic oligoadenylates stimulate additional defences in cells. Among these, cyclic oligoadenylate activated defence nucleases protect the cell by degrading RNA non-specifically, which slows down viral replication at the cost of cell growth. Uncontrolled RNA cleavage can be dangerous and potentially catastrophic, therefore off-switches are required to degrade the cyclic oligoadenylate alarm signal and deactivate defence enzymes if cells are to recover.

My work centres on mechanistic studies on cyclic oligoadenylate signalling and the discovery and characterisation of defence off-switches. Termed CRISPR ring nuclease, the cellular off-switches we have identified degrade cyclic oligoadenylates and deactivate defence enzymes to regulate the potency of the immune response.

In their battle for survival, viruses encode proteins to block CRISPR-Cas systems. These are known as Anti-CRISPRs. Remarkably, viruses have evolved their own anti-CRISPR ring nuclease variants. The anti-CRISPR ring nuclease degrades cyclic oligoadenylates much faster than the cellular counterpart and stops defence enzymes being activated. This gives viruses the upper hand; allowing them to propagate despite being detected by the cell.

The billion year war between prokaryotes and their viruses continue, and our study of their arsenals, used in offence and for defence, continue to uncover new tools that can be repurposed for biotechnology and medicine.[source: Symbiosis]

Mr Januka Athukoralage
Biomedical Sciences Building
University of St Andrews
North Haugh
St Andrews
KY16 9ST
Fife
UK

Related Content:

research@st-andrews
School of Biology
Biology Equality and Diversity Committee

Symbiosis Profile Page
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Graham, Dr Shirley: Research Technician Lab Manager

tel: 01334 463419/3436
fax:
room: B313 Annexe
email: sg71@st-andrews.ac.uk

Selected Publications

  1. A Type III CRISPR Ancillary Ribonuclease Degrades its Cyclic Oligoadenylate Activator Athukoralage JS, Graham S, Grüschow S, Rouillon C, White MF Journal of Molecular Biology 431(15) Jun 2019
  2. Investigation of the cyclic oligoadenylate signalling pathway of type III CRISPR systems. Rouillon C, Athukoralage JS, Graham S, Grüschow S, White MF Methods in Enzymology 616, January 2019
  3. Ring nucleases deactivate type III CRISPR ribonucleases by degrading cyclic oligoadenylate. Athukoralage JS, Rouillon C, Graham S, Grüschow S, White MF Nature 561(772) Oct 2018
  4. Control of cyclic oligoadenylate synthesis in a type III CRISPR system. Rouillon C, Athukoralage JS, Graham S, Grüschow S, White MF eLife Sciences 7 Jul 2018.
  5. Prespacer processing and specific integration in a Type I-A CRISPR system. Rollie C, Graham S, Rouillon C, White MF. Nucleic Acids Research 46(3) Dec 2017
  6. Multiple nucleic acid cleavage modes in divergent type III CRISPR systems. Zhang J, Graham S, Tello A, Liu H, White MF. Nucleic Acids Research 44(4). Jan 2016
  7. Cas6 specificity and CRISPR RNA loading in a complex CRISPR-Cas system. Sokolowski RD, Graham S, White MF, Nucleic Acids Research 42(10) Apr 2014.
  8. Structure of the CRISPR Type IIIA Effector Complex: conservation of form and function with type I systems. Rouillon C, Zhou M, Zhang J, Politis A, Beilsten V, Cannone G, Graham S, Robinson CV, Spagnolo L, White MF. Molecular Cell 52(1) Oct 2013.

[source: Symbiosis]

Dr Shirley Graham
Biomolecular Sciences Building
University of St Andrews
North Haugh
St Andrews
KY16 9ST
Fife
UK

Related Content:

research@st-andrews
School of Biology
Biomedical Sciences Research Complex

Symbiosis Profile Page
edit sg71 detailsData from research@st-andrews is not currently available for sg71.[source: research@st-andrews]


Dr Sabine Gruschow
Biomolecular Sciences Building University of St Andrews
North Haugh
St Andrews
KY16 9ST
Fife
UK

Related Content:

research@st-andrews
School of Biology

Symbiosis Profile Page
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Petrovic-Stojanovska, Mrs Biljana: Research Technician

tel: 01334 463436/3419
fax:
room: Annex Level 3
email: bp20@st-andrews.ac.uk

Mrs Biljana Petrovic-Stojanovska
Biomolecular Sciences Building
University of St Andrews
North Haugh
St Andrews
KY16 9ST
Fife
UK

Related Content:

research@st-andrews
School of Biology
Biomedical Sciences Research Complex

Symbiosis Profile Page
edit bp20 detailsData from research@st-andrews is not currently available for bp20.[source: research@st-andrews]


Zhu, Mr Wenlong: Postgraduate Student

tel: 3436
fax:
room: Annex
email: wz29@st-andrews.ac.uk

[source: research@st-andrews]

Mr Wenlong Zhu
Biomedical Sciences Building University of St Andrews
North Haugh
St Andrews
KY16 9ST
Fife
UK

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research@st-andrews
School of Biology

Symbiosis Profile Page
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