Research Description

Structural Biology of Protein Complexes

Our research centers on the study of protein structure and molecular recognition, with an emphasis on understanding protein-protein, protein-peptide and protein-lipid interactions.

Transcriptional repression complexes

Transcriptional regulation complexes are large, multicomponent  assemblies involving proteins with various enzymatic activities, adaptor  functions and DNA recognition modules. We are looking at interplay  between the components of these assemblies in order to understand the  structural “logic” of how these complexes carry out intricate biological  activities.

We are studying a family of BTB-zinc finger transcriptional regulators  that include proteins implicated in development and/or in cancer. In  these proteins, the BTB domain is a protein-protein interaction module  that recruits activator and/or corepressor complexes to promoter sites  recognized by the C-terminal zinc-finger regions. Our objective is to  understand and characterize the protein-protein interaction network of  these proteins.

For example, we have determined crystal structures of complexes between  the BTB domain of BCL6 and the minimal binding region of the SMRT, NCoR  and BCoR corepressors. BCL6 is a key oncoprotein in B-cell lymphoma and  exerts its biological effects through its interactions with  HDAC-associated corepressor complexes.  The structures reveal a peptide  binding groove on the side of the BCL6 BTB domain dimer that forms the  binding site for the corepressors. This detailed atomic view of the  interactions between the two proteins identifies a key pocket that can  be targeted with small molecule inhibitors.

Assembly and function of ubiquitin ligase E3 complexes

In addition to transcription, a key regulatory mechanism for the  control of cellular programs involves the targeted modification of  proteins with ubiquitin and ubiquitin-like proteins. One of the largest  families of proteins involved with this process are the  Cullin3-Ring-Ligases (CRL3s). This E3 ligase family uses  Cullin3/Rbx2/BTB adaptor protein complexes to bring a ubiquitin-charged E2 protein together with a substrate protein destined for  ubiquitination. Driven by BTB domain self-association, the CRL3s  assemble with multiple copies of each of the protein components. This  produces complexes with multiple E2~ubiqutin binding sites and multiple  substrate binding sites, and we are studying how the multivalent  architecture of the CRL3s affect substrate ubiquitination.

Structural biology of proteins involved in sphingolipid metabolism

Another area of focus in the lab is the mechanism of sphingolipid  metabolism in the cell. Sphingolipids have roles in cell integrity and  cell-cell recognition but can also can act as signaling molecules in  cell growth and apoptosis. As a result, lipids such as ceramide and  sphingosine-1-phospate have been implicated in tumor promotion.
Sphingolipids are in constant flux in cells, and the enzymes that modify  and breakdown these lipids generally require a “sphingolipid activator  protein”, or saposin. These saposin proteins interact with both  membranes and proteins to assemble catalytically active complexes, and  we are interested in the mechanism of the saposin activation reaction.
The small saposin proteins can access a surprisingly wide range of  physical states with lipids, bilayers and proteins. Some saposins act as  “physiological  detergents” and can solubilize target sphingolipids,  while others assemble membrane-bound enzyme complexes at the bilayer  surface in a form of interfacial catalysis.

Publications

View all publications on PubMed

Structure of Human Acid Sphingomyelinase Reveals the Role of the Saposin Domain in Activating Substrate Hydrolysis.
Xiong ZJ, Huang J, Poda G, Pomès R, Privé GG.
J Mol Biol. 2016 Jul 31;428(15):3026-42.  Read

Structural Insights into KCTD Protein Assembly and Cullin3 Recognition.
Ji AX, Chu A, Nielsen TK, Benlekbir S, Rubinstein JL, Privé GG.
J Mol Biol. 2016 Jan 16;428(1):92-107.  Read

Picodiscs for facile protein-glycolipid interaction analysis.
Leney AC, Rezaei Darestani R, Li J, Nikjah S, Kitova EN, Zou C, Cairo CW, Xiong ZJ, Privé GG, Klassen JS.
Anal Chem. 2015 Apr 21;87(8):4402-8.  Read

Ubiquitylome analysis identifies dysregulation of effector substrates in SPOP-mutant prostate cancer.
Theurillat JP, Udeshi ND, Errington WJ, Svinkina T, Baca SC, Pop M, Wild PJ, Blattner M, Groner AC, Rubin MA, Moch H, Privé GG, Carr SA, Garraway LA.
Science. 2014 Oct 3;346(6205):85-9.  Read

Adaptor protein self-assembly drives the control of a cullin-RING ubiquitin ligase.
Errington WJ, Khan MQ, Bueler SA, Rubinstein JL, Chakrabartty A, Privé GG.
Structure. 2012 Jul 3;20(7):1141-53  Read

Structure of saposin A lipoprotein discs.
Popovic K, Holyoake J, Pomès R, Privé GG
Proc Natl Acad Sci U S A. 2012 Feb 21;109(8):2908-12  Read

PagP crystallized from SDS/cosolvent reveals the route for phospholipid access to the hydrocarbon ruler.
Cuesta-Seijo JA, Neale C, Khan MA, Moktar J, Tran CD, Bishop RE, Pomès R, Privé GG.
Structure. 2010 Sep 8;18(9):1210-9  Read

A small-molecule inhibitor of BCL6 kills DLBCL cells in vitro and in vivo.
Cerchietti LC, Ghetu AF, Zhu X, Da Silva GF, Zhong S, Matthews M, Bunting KL, Polo JM, Farès C, Arrowsmith CH, Yang SN, Garcia M, Coop A, Mackerell AD Jr, Privé GG, Melnick A.
Cancer Cell. 2010 Apr 13;17(4):400-11.  Read

Crystal structure of a self-assembling lipopeptide detergent at 1.20 A.
Ho DN, Pomroy NC, Cuesta-Seijo JA, Privé GG.
Proc Natl Acad Sci U S A. 2008 Sep 2;105(35):12861-6.  Read

Structure of a BCOR corepressor peptide in complex with the BCL6 BTB domain dimer.
Ghetu AF, Corcoran CM, Cerchietti L, Bardwell VJ, Melnick A, Privé GG.
Mol Cell. 2008 Feb 15;29(3):384-91  Read

Sequence and structural analysis of BTB domain proteins.
Stogios PJ, Downs GS, Jauhal JJ, Nandra SK, Privé GG.
Genome Biol. 2005;6(10):R82  Read

Mechanism of SMRT corepressor recruitment by the BCL6 BTB domain.
Ahmad KF, Melnick A, Lax S, Bouchard D, Liu J, Kiang CL, Mayer S, Takahashi S, Licht JD, Privé GG
Mol Cell. 2003 Dec;12(6):1551-64.  Read