BSCB Newsletter, Autumn 2008

FASEB Summer Research Conference – Ubiquitin and Cellular Regulation
15-20 June 2008.  Vermont Academy, Saxtons River, Vermont, USA

The little town of Saxtons River, VT (population 519 in 2000 US Census), was largely unaware of the 180 scientists that arrived at the Vermont Academy on the afternoon of the 15th June.  However, this quiet and remote town proved to be the ideal location for the fostering of a familial environment in which PhD students, postdocs, and principal investigators alike could casually converse about past research, the status quo, and the future directions of this diverse and exciting field.

The conference goers were inducted into the world of ubiquitin by talks from three of the godfathers of this branch of biological science – Avram Hershko, Aaron Ciechanover (both at Technion, Israel Centre of Technology, Haifa, Israel), and Arthur Haas (Louisiana State University School of Medicine). All three played critical roles in defining the role of ubiquitin in intracellular ATP-dependent protein degradation, with Hershko and Ciechanover receiving the Nobel Prize in Chemistry in 2004 for their work.  Hershko was unable to attend the conference in person, instead, a video recorded interview of Hershko by Michael Glickman (Technion-Israel Institute of Technology) was shown which took us through some of the pivotal steps made in the discovery of ubiquitin and also provided some words of wisdom and advice to all new and aspiring scientists as to how to proceed in our academic lives.

From Monday morning until Friday afternoon the schedule was jam-packed with talks and poster sessions. Like many other poster presenters, I had to stand by my posters for nearly four hours on the Monday, leaving me slightly hoarse and totally drained after having to compete with all the other poster presenters for the attention of passers-by, and having to speak loudly above all the excited voices.

The talks themselves were of an extremely high calibre, leaving a young aspiring scientist as myself inspired and at times a bit overawed. Brenda Shulman (St. Jude Children’s Research Hospital) gave a very structure-based presentation on how the modification of a Cullin E3 ligase complex is activated by its modification with NEDD8, a ubiquitin-like (Ub-L) molecule which causes a conformational change and allows the E3 complex to conjugate ubiquitin to its substrates. The very focussed work on this protein complex gave a beautiful example of how powerful structure-determining techniques such as X-ray crystallography can give an insight into the functional control of individual proteins and protein complexes.  Similarly, Shuya Fukia (University of Tokyo, Japan) produced a very high resolution structure for the JAMM catalytic domain of AMSH (a deubiquitinating enzyme, DUB, associated with EGF receptor downregulation) complexed with a Lys63 linked di-Ubiquitin molecule, which provided structural evidence as to the specificity of this DUB towards this type of linked chain, and was the first example of a complex structure of this type. 

 The proteasome was also heavily discussed. Although this enormous complex responsible for the degradation of cellular and ER-associated proteins has been studied for numerous years, there is still a lot unknown about its assembly and composition.  Mark Hochstrasser (Yale University) and members of his laboratory are using a split-Ubiquitin system to study proteasomal assembly in vivo in yeast cells, and the role of two chaperone proteins named PAC1 and PAC2 appear critical in the process. Michael Glickman (Technion-Israel Institute of Technology) and Alfred Goldberg (Harvard Medical School) both presented their work involving substrate recruitment and subsequent translocation into the proteasomal core. Glickman’s lab have discovered a molecular stent composed of a multimeric complex made up of a ring of Rpn1 and Rpn2 subunits which sits within the 19S regulatory particle of the proteasome and plays an important role in channel gating.  Goldberg’s presentation focused on the motifs of the 19S regulatory lid that insert into the 20S core particle and are essential for gate opening. Andreas Matouschek (Northwestern University) gave a fascinating talk on substrate recognition by the proteasome in which he described how his laboratory had been feeding different artificially created substrates to recombinant proteasomes to assess the requirement of particular structures and/or sequences for the initiation of degradation.  His conclusions that the proteasome requires its substrates to have an unstructured extension relatively near to the site of ubiquitination of at least 30 amino acids and of a certain level of complexity in its amino acid composition shed some light on how the proteasome selectively degrades certain subunits of protein complexes, and how it has evolved to be able to degrade such a large number of different cellular proteins.

Stephen Elledge and Wade Harper (both at Harvard Medical School) presented their recent work on large-scale cellular studies, Elledge using the “GPS system” for measuring regulated protein turnover, and Harper using pull-downs of TAP-tagged DUBs to assess the protein complexes to which they are associated. Their work was heavily supported by Steven Gygi (Harvard Medical School, Boston, MA, USA), a conference star in absentia, as his work in the development of the so-called absolute quantification (AQUA) method of mass spectrometry, which allows the measurement of frequency of monoubiquitination and various polyubiquitin chain linkages, has been utilised extensively.  

A special mention also needs to be made to Heran Darwin’s (NYU School of Medicine) revelations of the discovery of a Ub-L in Mycobacterium tuberculosis, a finding that is not only interesting from an evolutionary point of view because this is the lowest species in which a Ub-L has been discovered, but also from a clinical point of view as it may present avenues for tackling tuberculosis .

The conference was a fantastic experience, and I would highly recommend it to anyone interested in the ubiquitin field. I would like to heartily thank the BSCB for awarding me an Honor Fell Travel Grant so that I could attend the conference. 

Sebastian Daniel Hayes,
The Physiological Laboratory
The University of Liverpool.