SUMO proteomics in C. elegans; germ line, meiosis and the DNA damage response

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Proteins need to be regulated to properly fulfil their function in cells and living organisms. Specialized sets of proteins are required to convey a variety of signals within living cells. Such signalling proteins confer signals by attaching distinct sets of molecules to their target proteins. The attachment of such molecules, referred to as modification serves as a 'cellular language'. Modern molecular biology research focuses on such signalling proteins and tries to address their importance in modifying the activity of their targets. Modifications that confer signals such as phosphorylation or ubiquitylation have been known for a long time. However, only in the past decade, it became clear that sumoylation provides an important way of intracellular communication. The Hay laboratory elaborated important molecular details pertaining to basic biochemical reactions that are needed for SUMO modification. SUMO by itself is a sizable protein, that is attached to certain residues of its target proteins and several proteins are needed to confer sumoylation. So called 'systems approaches' aim to provide a comprehensive analysis and understanding of the 'SUMO language'. Such analysis requires the identification, of all SUMO modified proteins, and a detailed analysis of how and to which extend SUMO modification changes in response to various physiological and pathophysiological conditions. First experiments to assess the global role of SUMO modification were done in with cell cultures. While those systems have obvious experimental advantages, these cells do not necessarily reflect the behaviour of cells in intact organisms. This is why we plan to use the small roundworm C. elegans as a model system to globally asses the extend, and importance of sumoylation in a living organism. C. elegans was chosen as the simplest possible animal system. Studies are facilitated by the simplicity of the organism at the developmental and anatomical level, by the ease of its maintenance, as well as by the availability of methods that allow for manipulating its genetic information procedures necessary to study the importance of SUMO modification. Despite of its simplicity, C. elegans is a multicellular organism that shares many fundamental genetic programs with humans. Thus results obtained in the C. elegans system are likely to be applicable to humans and working with worms does not raise ethical concerns. As part of our studies we want to express modified versions of SUMO in the worm, such that we can best apply the advanced methods we have developed to isolate all SUMO modified proteins. To identify those proteins, but also to assess the extent of SUMO modification we will use a method we recently developed allowing for the identification and quantification of thousands of worm proteins. We not only want to find all SUMO modified proteins, but also want to assess the importance of SUMO modification. To start with this, we chose an important biological processes extensively studied in our labs. 1) Meiosis is a specialised cell division, needed for the generation of germ cells. During this division the duplicated set of chromosomes occurring in normal cells is reduced to just one copy. The subsequent fusion of germ cell restores a duplicated set of chromosomes one coming from the father, another one coming from the mother. Not only this, during meiosis a process referred to as recombination also mixes individual chromosomes such that chromosomes contain elements from both grandparents. Recombination ensures genetic diversity. 2) Recombination pertains to the breaking and linking DNA molecules. Recombination is used when DNA damaging agents such as ionizing irradiation breaks chromosomes. We already have know that SUMO modification is important for meiosis and recombination and we now want perform a systematic analysis of this. Our studies are important to understand how the genetic information is passed on from one generation to the next.