What is new in the nucleolus?

This EMBO Workshop on the Nucleolus: New Perspectives took place between 27 and 29 March 2006, in York, UK, and was organized by J. Wainwright, C. Rubbi, J. Milner and J. Hiscox.![][1] York, UK, was a good choice for the venue of this workshop because the history of nucleolar research—like the city—falls into distinct eras. Founded by the Romans in 71 ad, York has been occupied at various points in time by the Saxons, Vikings and Normans. Our understanding of the nucleolus has also followed a pattern in which rapid advances have been interspersed with periods of relative dormancy. The nucleolus was first observed early in the nineteenth century, but it was not until the 1960s that its role in ribosome biogenesis was established. After that, it was assumed that the nucleolus did not do much else; however, to our surprise, many unexpected roles for the nucleolus have emerged in the past decade.We now have working catalogues of the components of human and plant ( Arabidopsis ) nucleoli. A few years ago, collaboration between the laboratories of A. Lamond (Dundee, UK) and M. Mann (Odense, Denmark) led to the first major nucleolar proteomic study. Since then, at least 700 proteins have been identified in human nucleoli (Leung et al , 2006). Combining mass spectrometry with stable isotope labelling techniques, the Lamond group has also examined the redistribution kinetics of nucleolar proteins after drug treatment. For example, Lamond showed that actinomycin D causes some proteins to accumulate in the nucleolus, and others to redistribute to the nucleoplasm. Surprisingly—in response to treatment with the proteasome inhibitor MG132—ribosomal proteins accumulate in the nucleolus. Lamond interprets this to mean that the cell has a surplus of ribosomal proteins that are ready for an upregulation of ribosomal DNA transcription. In cells with lower rates of transcription, excess … [1]: /embed/graphic-1.gif