The CRISPR system: a new frontier in prokaryotic molecular biology

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The battle between viruses and the cells they attempt to infect and subvert is one of the main driving forces in molecular evolution. Prokaryotes target and degrade invading DNA using 'restriction enzymes', the discovery of which revolutionised molecular biology. Eukaryotes, including humans, use the RNA interference (RNAi) pathway to target and degrade viral RNA. In the last few years a prokaryotic version of the RNAi pathway, the so-called CAS-CRISPR system, has come to light. Viral sequences are stored in the host genome as 'spacers' flanked by direct repeat sequences (CRISPRs). It is known that host cells incorporate new viral DNA into the CRISPRs, and that this confers immunity against future viral infection. The CRISPR system is envisaged to act in an analogous manner to the RNAi pathway A number of widely conserved 'Cas' proteins (up to 50 per genome) are associated with the CRISPR sequences, and these are thought to be responsible for CRISPR processing, viral defence and the incorporation of new viral sequences. The functions of these proteins are not clearly understood. We have the experience and technological know-how to study all the Cas proteins from the model organism Sulfolobus solfataricus. Cas protein structures will be solved, and Cas protein interactions delineated. The activities of individual Cas proteins and complexes will be determined using a variety of techniques in routine use in our laboratories. The ultimate aim is to acheive a molecular understanding of the CRISPR system. As well as providing fundamental new insights into prokaryotic biology, the work may lead to new methods to manipulate the genomes of useful organisms (synthetic biology) or to treatments for important microbial pathogens.