Vincenzo Costanzo Lecture
/in Lectures /by roberto-11112Vincenzo Costanzo
Abstract
Maintenance of genome integrity during DNA replication relies on several factors that do not directly participate in DNA synthesis. Among these there are proteins that respond to DNA lesions and structures impairing replication fork progression. These factors are believed to be particularly important for the resolution of DNA damage occurring during DNA replication and the faithful duplication of chromosome regions with complex or repetitive DNA sequences. In my group, we combine the power of the Xenopus egg extract with advanced imaging techniques based on transmission electron microscopy (EM) to study major DNA metabolism processes linked to DNA replication and DNA repair. This approach allowed us to uncover for the first time a role for RAD51 in protecting replication forks, by preventing Mre11 mediated processing of nascent DNA (Hashimoto et al 2010, NSMB). These findings have been confirmed in mammalian cells by several other studies and linked to cancer cell survival and sensitivity to chemotherapy. More recently, we have shown that extensive nascent DNA degradation is triggered by the formation of reversed forks at stalled replication intermediates operated by SNF2 helicases (Kolinjivadi et al 2017, Mol Cell). These pathways are likely to play a major role in the presence of DNA damage and at complex DNA loci, including the centromeres, which we have shown to be enriched for DNA repair factors (Aze et al 2016, NCB). This work will be discussed in light of recent results obtained on replication fork protection mechanisms.
Mechanisms of replication fork protection
Share this entry
Federico Forneris Lecture
/in Lectures /by roberto-11112Federico Forneris
Abstract
Synapse formation is a finely-tuned process requiring multiple steps and a variety of receptors and signaling molecules. The neuromuscular synapse or junction (NMJ) – the connection between motor neurons and skeletal muscles – represents the archetype junction system for studying synapse formation and conservation. NMJ formation requires coordinated interactions between motor neurons and muscle fibers, which ultimately result in the construction of a highly specialized postsynaptic architecture juxtaposed to a highly differentiated nerve terminal. Our research focuses on the investigation of the key signaling molecules and receptors that enable NMJ formation and stabilization. We study the extracellular architecture and function of two subsets of proteins tied to the role of agrin, a well known NMJ stabilizer. The first subset includes the agrin receptor, comprising the receptor tyrosine kinase MuSK (muscle-specific kinase) and its co-receptor LRP4; the second includes the soluble synapse-specific regulatory protease Neurotrypsin (NT) that cleaves agrin with high specificity. This focus has yielded novel insight into processes underlying NMJ formation. In the first case, crystal structures of MuSK ectodomain fragments, coupled with solution scattering data and cross-linking mass spectrometry, highlighted the contribution of molecular flexibility in receptor activation and signaling. In the second case, in vitro enzyme studies and cell-based assays elucidated the specificity of NT, revealing a delicate regulatory mechanism mediated by splicing variants, ion binding, and post-translational modifications. Our results offer new understanding of NMJ formation and stabilization, and contribute innovative tools to the characterization of this fundamental biological system.
Molecular architectures, interactions and functions of neuromuscular synapse organizers
Share this entry
Matteo Iannacone Lecture
/in Lectures /by roberto-11112Matteo Iannacone
Abstract
CD8+ T cell responses to hepatotropic viruses like HBV range from dysfunction to differentiation into effector cells, but the mechanisms underlying these distinct outcomes remain poorly understood. Here we show that priming by Kupffer cells –not natural targets of HBV – leads to differentiation into effector cells that form dense, extravascular clusters of rather immotile cells scattered throughout the liver. By contrast, priming by hepatocytes – natural targets of HBV – leads to local activation and proliferation but lack of differentiation into effector cells; these cells form loose, intravascular clusters of motile cells that coalesce around portal tracts. Transcriptomic and chromatin accessibility analyses unveil unique features of these dysfunctional CD8+ T cells, with limited overlap with those of exhausted or tolerant T cells; accordingly, CD8+ T cells primed by hepatocytes cannot be rescued by anti-PD-L1 treatment, but instead respond to IL-2. These findings suggest new immunotherapeutic strategies against chronic HBV infection.
Spatiotemporal dynamics and genomic landscape of CD8+ T cells undergoing intrahepatic priming
Share this entry
CONTACT
Armenise Harvard Foundation
180 Longwood Avenue
Suite 110-C
Boston, MA 02115
Telephone:
+1 617.432.6256