病毒与宿主细胞表面结合的方式 - Ari Helenius P1
本视频由科普中国和生物医学大讲堂出品
Ari Helenius (ETH Zurich) Part 1: Virus entry
Viruses are extremely simple and small yet they are responsible for many of the worlds diseases. A virus particle consists of only a genome, a protein coat or capsid, and sometimes a surrounding lipid envelope. To replicate, a virus must successfully enter a host cell, uncoat its genome, and appropriate the host cell machinery to replicate its genome and produce viral proteins. Part 1 of this lecture will discuss ways in which viruses bind to the surface of host cells. Simian Virus 40 which binds to specific cell surface glycolipids, and Human Papilloma Virus-16 which binds to sites on filoipodia, are examples of different binding mechanisms. Attachment of viruses to the plasma membrane activates cell signaling resulting in endocytosis of the viral particles. This lecture is appropriate for upper level undergraduate and graduate classes studying virology or endocytosis.
牛痘病毒如何进入细胞 - Ari Helenius P3
本视频由科普中国和生物医学大讲堂出品
Ari Helenius (ETH Zurich) Part 3: Open Sesame: Cell Entry and Vaccinia Virus
Part 3 focuses on a single virus, the Vaccinia virus, as a model for cell binding, signaling and endocytosis. Fluorescently labeled Vaccinia viruses bind to and surf along host cell filopodia. Helenius lab members noticed that when Vaccinia, unlike other viruses, reached the surface of the cell body it caused the plasma membrane to form blebs. Further experiments showed that the virus tricks the cell into thinking it is apoptotic debris. This induces blebbing and subsequent uptake of the virus by macropinocytosis. Additionally, automated high throughput siRNA screening was used to screen a large number of infected cells for host genes required for Vaccinia virus uptake. Analysis of the genes identified allowed host factors and processes critical to viral infection to be identified. Expansion of this technique may provide a new source of information on pathogen-host interactions.
病毒包膜的内吞和渗透作用 - Ari Helenius P2
本视频由科普中国和生物医学大讲堂出品
Ari Helenius (ETH Zurich) Part 2: Endocytosis and Penetration
In the second lecture, the next steps in viral infection are described. Endocytosis of plasma membrane bound viruses can occur via a number of mechanisms including caveolar, clathrin, non-clathrin, or lipid raft mediated pathways. The internalized virus is enclosed in an endosome that may undergo increasing acidification resulting in acid mediated fusion between the viral envelope and the vesicle membrane. Following membrane penetration, the virus, once again, makes use of cellular machinery such as microtubules and their motors, to transfer its genome to the nucleus. Helenius describes experiments from his lab and others that have deciphered these complex processes.
Controlling the Cell Cycle: Introduction - David O. Morgan
本视频由科普中国和生物医学大讲堂出品
David O. Morgan (UCSF) Part 1: Controlling the Cell Cycle: Introduction
Cells reproduce by duplicating their chromosomes and other components and then distributing them into a pair of genetically identical daughter cells. This series of events is called the cell cycle. In the first part of this lecture, I provide a general overview of the cell-cycle control system, a complex regulatory network that guides the cell through the steps of cell division. I briefly describe the major components of this regulatory system and how they fit together to form a series of biochemical switches that trigger cell-cycle events at the correct time and in the correct order.
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Controlling the Cell Cycle: Cdk Substrates - David O. Morgan
本视频由科普中国和生物医学大讲堂出品
David O. Morgan (UCSF) Part 2: Controlling the Cell Cycle: Cdk Substrates
Cyclin-dependent kinases (Cdks) are the central components of the control system that initiates the events of the cell cycle. In the second part of this lecture, I discuss my laboratory's efforts to address the problem of how the Cdks trigger cell-cycle events. I describe our methods for identifying the protein substrates of the Cdks, and I discuss how these studies have led to important clues about how Cdks find their correct targets in the cell and how phosphorylation of those targets governs their function.
Controlling the Cell Cycle: Anaphase Onset - David O. Morgan
本视频由科普中国和生物医学大讲堂出品
David O. Morgan (UCSF) Part 3: Controlling the Cell Cycle: Anaphase Onset
In the anaphase stage of the cell cycle, the duplicated chromosomes are pulled apart by a machine called the mitotic spindle, resulting in the distribution of a complete set of chromosomes to each of the daughter cells. In the third part of this lecture, I describe the combination of biochemistry and microscopy in my laboratory that led to the discovery of a regulatory switch that triggers the abrupt and synchronous separation of the chromosomes at the onset of anaphase.
布鲁斯·艾伯茨：learning from Failure
Alberts declares "Success doesn't really teach you much, failure teaches you a lot." Speaking from his personal experience, Alberts asserts that all scientists make mistakes and suffer setbacks but learning from those failures is what allows one ultimately to succeed.
Stability of Morphogen Gradients & Movement of Molecules
In my second lecture I describe experiments using EGFP tagged Bicoid to follow Bcd gradient establishment in living embryos, and to test various aspects of the simple model. Despite continuous synthesis of new Bcd protein at the anterior end of the egg, we find that the concentration of Bcd in nuclei at any given point along the anterior posterior axis is constant over time and is reproducible from embryo to the next. This reproducibility means that the gradient is sufficiently robust to provide positional information and thus can accurately direct gene activities. One the other hand, quantitative imaging experiments point to several features of the gradient that are hard to explain - how target genes activated by Bcd distinguish relatively subtle differences in low concentrations, and how Bcd molecules move from the anterior site of their synthesis to the site of their transcriptional activity. See more at http://www.ibioseminars.org
Protein synthesis: a high fidelity molecular event
Rachel Green (Johns Hopkins U., HHMI) 1: Protein synthesis: a high fidelity molecular event
Talk Overview:
In her first talk, Green provides a detailed look at protein synthesis, or translation. Translation is the process by which nucleotides, the “language” of DNA and RNA, are translated into amino acids, the “language” of proteins. Green begins by describing the components needed for translation; mRNA, tRNA, ribosomes, and the initiation, elongation, and termination factors. She then explains the roles of these players in ensuring accuracy during the initiation, elongation, termination and recycling steps of the translation process. By comparing translation in bacteria and eukaryotes, Green explains that it is possible to determine which components and steps are highly conserved and predate the divergence of different kingdoms on the tree of life, and which are more recent adaptations.
Green’s second talk focuses on work from her lab investigating how ribosomes detect defective mRNAs and trigger events leading to the degradation of the bad RNA and the incompletely translated protein product and to the recycling of the ribosome components. Working in yeast and using a number of biochemical and genetic techniques, Green’s lab showed that the protein Dom34 is critical for facilitating ribosome release from the short mRNAs that result from mRNA cleavage. Experiments showed that Dom34-mediated rescue of ribosomes from short mRNAs is an essential process for cell survival in higher eukaryotes.
Speaker Biography:
Rachel Green received her BS in chemistry from the University of Michigan. She then moved to Harvard to pursue her PhD in the lab of Jack Szostak where she worked on designing catalytic RNA molecules and investigating their implications for the evolution of life. As a post-doctoral fellow at the University of California, Santa Cruz, Green began to study how the ribosome translates mRNA to protein with such accuracy.
Currently, Green is a Professor of Molecular Biology and Genetics at the Johns Hopkins School of Medicine and an Investigator of the Howard Hughes Medical Institute. Research in her lab continues to focus on the ribosome and factors involved in the fidelity of eukaryotic and prokaryotic translation.
Green is the recipient of a Johns Hopkins University School of Medicine Graduate Teaching Award as well as the recipient for numerous awards for her research. She was elected to the National Academy of Sciences in 2012.
People coming together makeing a difference
People coming together makeing a difference