Biomedical subjects

Bruce T Seet

Publications and source records attributed to Bruce T Seet.

8 recordsLinked to original sources

PubMed2006

Reading protein modifications with interaction domains.

Proteins are controlled by a vast and dynamic array of post-translational modifications, many of which create binding sites for specific protein-interaction domains. We propose that these domains, working together, read the state of the proteome and therefore couple post-translational modifications to cellular organization. We also identify common strategies through which modification-dependent interactions synergize to regulate cell behaviour.

Amino Acid Motifs↗

PubMed2005

A structure-based model of the c-Myc/Bin1 protein interaction shows alternative splicing of Bin1 and c-Myc phosphorylation are key binding determinants.

The N terminus of the c-Myc oncoprotein interacts with Bin1, a ubiquitously expressed nucleocytoplasmic protein with features of a tumor suppressor. The c-Myc/Bin1 interaction is dependent on the highly conserved Myc Box 1 (MB1) sequence of c-Myc. The c-Myc/Bin1 interaction has potential regulatory significance as c-Myc-mediated transformation and apoptosis can be modulated by the expression of Bin1. Multiple splicing of the Bin1 transcript results in ubiquitous, tissue-specific and tumor-specific populations of Bin1 proteins in vivo. We report on the structural features of the interaction between c-Myc and Bin1, and describe two mechanisms by which the binding of different Bin1 isoforms to c-Myc may be regulated in cells. Our findings identify a consensus class II SH3-binding motif in c-Myc and the C-terminal SH3 domain of Bin1 as the primary structure determinants of their interaction. We present biochemical and structural evidence that tumor-specific isoforms of Bin1 are precluded from interaction with c-Myc through an intramolecular polyproline-SH3 domain interaction that inhibits the Bin1 SH3 domain from binding to c-Myc. Furthermore, c-Myc/Bin1 interaction can be inhibited by phosphorylation of c-Myc at Ser62, a functionally important residue found within the c-Myc SH3-binding motif. Our data provide a structure-based model of the c-Myc/Bin1 interaction and suggest a mode of regulation that may be important for c-Myc function as a regulator of gene transcription.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Regulation of Smurf2 ubiquitin ligase activity by anchoring the E2 to the HECT domain.

The conjugation of ubiquitin to proteins involves a cascade of activating (E1), conjugating (E2), and ubiquitin-ligating (E3) type enzymes that commonly signal protein destruction. In TGFbeta signaling the inhibitory protein Smad7 recruits Smurf2, an E3 of the C2-WW-HECT domain class, to the TGFbeta receptor complex to facilitate receptor degradation. Here, we demonstrate that the amino-terminal domain (NTD) of Smad7 stimulates Smurf activity by recruiting the E2, UbcH7, to the HECT domain. A 2.1 A resolution X-ray crystal structure of the Smurf2 HECT domain reveals that it has a suboptimal E2 binding pocket that could be optimized by mutagenesis to generate a HECT domain that functions independently of Smad7 and potently inhibits TGFbeta signaling. Thus, E2 enzyme recognition by an E3 HECT enzyme is not constitutively competent and provides a point of control for regulating the ubiquitin ligase activity through the action of auxiliary proteins.

Amino Acid Motifs↗

PubMed2004

MAPK signaling: Sho business.

Sho1 is a membrane protein in yeast that activates the Hog MAPK signaling pathway in response to high osmolarity. An accumulating body of work has focused on Sho1 as a model to better understand the mechanisms that dictate signaling specificity.

Membrane Proteins↗

PubMed2004

Interaction analysis of viral cytokine-binding proteins using surface plasmon resonance.

Surface plasmon resonance (SPR) biosensors have become an increasingly popular technology for characterizing the protein-protein interactions of virus-host interactions. Various studies have exploited the versatility of SPR to probe the interaction between virus and host components, including constituents of virus particles and host cellular receptors, as well as interactions between viral proteins and host immune molecules. This chapter describes basic procedures for employing SPR to study the interaction between poxvirus proteins and host immune-signaling proteins. We also identify how this methodology may be adapted toward other applications relevant in the study of poxvirus-host interactions.

Biosensing Techniques↗

PubMed2003

Analysis of an orf virus chemokine-binding protein: Shifting ligand specificities among a family of poxvirus viroceptors.

We identify a secreted chemokine inhibitor encoded by orf virus (ORFV), the prototypic poxvirus of the Parapoxvirus genus, and show that it is related to the poxvirus type II CC-chemokine-binding proteins (CBP-II) produced by members of the Orthopoxvirus and Leporipoxvirus genera. The ORFV chemokine-binding protein (CBP) is functionally similar to the CBP-II proteins in its ability to bind and inhibit many CC-chemokines with high affinity. However, unlike CBP-II, the ORFV CBP also binds with high affinity to lymphotactin, a member of the C-chemokine family, demonstrating that the ORFV CBP possesses an altered binding specificity. Interestingly, the amino acid sequence of ORFV CBP more closely resembles the granulocyte-macrophage colony-stimulating factor/IL-2 inhibitory factor also produced by ORFV, implicating the granulocyte-macrophage colony-stimulating factor/IL-2 inhibitory factor protein as a highly diverged, but related, member of the CBP-II protein family. Notably, these findings suggest that the genes that encode these proteins derive from a common poxvirus ancestral gene that has since been modified in binding specificity during speciation of the poxvirus genera. Overall, these findings illustrate the concept of evolution of viral proteins at the biophysical and molecular interface.

Amino Acid Sequence↗

PubMed2002

Viral chemokine-binding proteins.

The chemokines are a large family of small signaling proteins that bind to G-protein-coupled receptors (GPCRs) on target cells and mediate the directional migration of immune cells into sites of infection or inflammation. The large DNA viruses, particularly the poxviruses and herpesviruses, have evolved several mechanisms to corrupt the normal functioning of the chemokine network. Two strategies rely on mimicking chemokines or chemokine receptors. A third strategy involves the production of secreted chemokine-binding proteins (CKBPs) that exhibit no sequence similarity to any known host proteins, yet function to competitively bind and inhibit the interactions of chemokines with cognate receptors. Each strategy has provided unique insights into the elusively complex world of the chemokines. Here, we focus on recent advances made in the understanding of secreted CKBPs encoded by poxviruses and herpesviruses. A better understanding of how viral CKBPs function to manipulate the immune response may provide further clues as to how to develop specific therapeutic agents to abrogate chemokine-mediated disease conditions.

Amino Acid Sequence↗

PubMed2001

Poxviruses and immune evasion.

Large DNA viruses defend against hostile assault executed by the host immune system by producing an array of gene products that systematically sabotage key components of the inflammatory response. Poxviruses target many of the primary mediators of innate immunity including interferons, tumor necrosis factors, interleukins, complement, and chemokines. Poxviruses also manipulate a variety of intracellular signal transduction pathways such as the apoptotic response. Many of the poxvirus genes that disrupt these pathways have been hijacked directly from the host immune system, while others have demonstrated no clear resemblance to any known host genes. Nonetheless, the immunological targets and the diversity of strategies used by poxviruses to disrupt these host pathways have provided important insights into diverse aspects of immunology, virology, and inflammation. Furthermore, because of their anti-inflammatory nature, many of these poxvirus proteins hold promise as potential therapeutic agents for acute or chronic inflammatory conditions.

Animals↗