Biophysical Society Thematic Meeting - November 16-20, 2015

Biophysics in the Understanding, Diagnosis, and Treatment of Infectious Diseases Speaker Abstracts

Super Resolution Microscopy Reveals a Preformed NEMO Lattice Structure that is Collapsed in a Genetic Disease Musa Mhlanga . CSIR Biosciences, Pretoria, South Africa. The NF-κB pathway is one of most important signaling cascades in various living organisms, with critical roles in cancer and the immune and inflammatory response. In clinical settings, it has therefore become increasingly necessary to understand the mechanism of disease caused by mutations in genes of this pathway. However, certain aspects of this cascade, notably the rapidity and efficiency with which it is executed remain unexplained. Several lines of evidence have led to the hypothesis that the regulatory/sensor protein NEMO is responsible for this efficiency by acting as a binary switch that depends on polyubiquitin chains. In this study,we use super- resolution microscopy to visualize the existence in non-stimulated cells of higher-order NEMO lattice structures dependent on the presence of polyubiquitin chains, which allow proximity based trans-autophosphorylation leading to cooperative activation of the signaling cascade. We also show that NF-κB activation results in both qualitative and quantitative modification of these structures. These data evoke the formation of higher order structures in signal transduction as key insulators of noise in signal transduction cascades, permitting Hill function responses to external stimuli.

Open Access Chemical Probes of Chromatin Regulators Cheryl Arrowsmith . University of Toronto, Toronto, Canada.

Regulation of gene expression via chromatin associated factors and alterations of the cellular epigenome are fundamental to most biological processes, to many disease mechanisms and to host-pathogen interactions and immune evasion. We are taking a protein family approach to understand how chromatin regulatory proteins recognize specific histone tail sequences and their posttranslational modifications. Proteins such as histone methyltransferases, demethylases, acetyltransferases and bromodomains and chromodomains mediate nuclear signaling networks that regulate epigenetic cellular states and gene expression programs. Systematic structural and biophysical analyses of these human and parasite protein families and their binding partners are revealing key features of selectivity and regulation among these factors, enabling structure-based development of potent, selective, cell-active small molecule inhibitors of individual epigenetic regulatory proteins. I will describe the various biophysical methods we use for characterizing human and parasite epigenetic regulators and provide examples of their manipulation in human cells using selective epigenetic chemical probes.

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