Research Interests:

Post-translational modification of lysine residues plays a central role in numerous biological processes. Our research centers on two examples of lysine modification: the Sir2 class of NAD+-dependent deacetylases and the assembly and recognition of linkage-specific polyubiquitin chains. We use x-ray crystallography, together with biochemical, biophysical and genetic analysis, to gain insight into the enzymatic mechanisms and protein-protein interactions underlying these processes.

Acetylation of lysine residues plays a regulatory role in many processes, most notably in the regulation of mRNA transcription. The Sir2 enzymes, known as sirtuins, are NAD+-dependent deacetylases that regulate numerous processes such as transcriptional silencing in yeast, lifespan regulation, fat mobilization, and enzyme activity. We use a combination of crystallography and biochemical analysis to study the enzymatic mechanism and how it is regulated by inhibitors and metabolites. We are also studying how yeast Sir2 is recruited to telomeres as part of a complex that includes Rap1. Some sirtuins also catalyze a related reaction known as ADP ribosylation, and we are exploring the basis for the switch between these two reactions.

The attachment of the small protein, ubiquitin, to lysine residues serves a variety of signaling functions. The ubiquitin modification can consist of a single ubiquitin or a polyubiquitin chain in which the C-terminus of one ubiquitin is covalently linked to one of seven lysine residues on the next. The particular linkage type determines biological function: K48-linked polyubiquitin chains target proteins for destruction by the proteasome, whereas K63-linked chains play a non-degradative role in DNA damage tolerance and NF-kB activation. We study the structural basis for both the assembly and disassembly of linkage-specific polyubiquitin chains, as well as the way in which particular chain topologies are recognized in the cell.

Publications:

A.P. VanDemark, R.M. Hofmann, C. Tsui, C.M. Pickart and C. Wolberger (2001) Molecular insights into polyubiquitin chain assembly: crystal structure of the Mms2/Ubc13 heterodimer. Cell Jun 15;105(6):711-20.
PubMed Abstract

C. Garvie, J. Hagman and C. Wolberger (2001) Structural studies of Ets-1/Pax5 complex formation on DNA. Mol Cell Dec;8(6):1267-76.
PubMed Abstract

J. Avalos, I. Celic, S. Muhammad, M. Cosgrove, J. Boeke and C. Wolberger (2002) Structure of a Sir2 enzyme bound to an acetylated p53 peptide. Mol. Cell, 10, 523-535.
PubMed Abstract

J. Avalos, J. Boeke and C. Wolberger (2004) Structural basis for the mechanism and regulation of Sir2 enzymes. Molecular Cell 12, 639-648.
PubMed Abstract

Avalos J.L., K.M. Bever, and C. Wolberger. (2005) Mechanism of sirtuin inhibition by nicotinamide: altering the NAD(+) cosubstrate specificity of a Sir2 enzyme. Mol Cell. 17:855-868.
PubMedAbstract

M.J. Eddins, C.M. Carlile, K.M. Gomez, C.M. Pickart and C. Wolberger (2006), “Mms2/Ubc13 covalently bound to ubiquitin: structural basis of linkage-specific polyubiquitin chain formation,” Nature Structural and Molecular Biology 13, 915-920.
PubMedAbstract

M.J. Eddins, R. Varadan, D. Fushman, C.M. Pickart and C. Wolberger (2007), “Crystal structure and solution NMR studies of Lys48-linked tetraubiquitin at neutral pH,” Journal of Molecular Biology 367, 204-211

W.F. Hawse , K.G. Hoff, D. Fatkins , A. Daines, O.V. Zubkova, V.L. Schramm , W. Zheng, and C. Wolberger (2008), “Structural Insights Into Intermediate Steps in the Sir2 Deacetylation Reaction,” Structure 16, 1368-1377.

Complete List of Publications