49 / 101
Biophysics in the Understanding, Diagnosis, and Treatment of Infectious Diseases Speaker Abstracts
44
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.