1、Breakthrough in 1950s The viral nucleic acid genome carries the information needed to replicate,build,and spread virions in the world.One of the building blocks of Molecular Biology T4,TMVHershey-Chose experimentwith phage T4Fraenkel-Conrats work with TMVSeven Genome Types Either DNA or RNA Structur
2、ally diverse:linear,circular,segmented,gapped,single-stranded(+)strand,single-stranded(-)strand,single stranded(ambisense),double-stranded,some have covalently attached proteins,some have cross-linked ends of double-stranded DNA RNA World hypothesisWhat information is encoded in a viral genome？Repli
3、cation of viral genome Assembly and packaging of the genome Regulation and timing of the replication cycle Modulation of host defenses Spread to other cells and hostsInformation Not contained in viral genomes No genes encoding the complete protein synthesis machinery No genes encoding protein involv
4、ed in energy production or membrane biosynthesis No classical centromeres or telomeres found in standard host chromosomesThe Baltimore System Viral genome must make mRNA that can be read by host ribosomes NOT all(+)RNA is mRNA Each way has unique polymerase,primer,template and termination requiremen
5、ts Each virus family has its own characteristic genome strategySeven classes distinguished by genome replication strategiesds DNA,ss DNAds RNA,+ss RNA,-ssRNA,RetrodsDNA genomes The problem of replicating the ends of linear DNA molecules through the use of RNA primers.Circular ds DNA genomes that are
6、 replicated in the nucleusLinear ds DNA genomes that are replicated in the nucleusLinear ds DNA genomes that are replicated in the nucleusThe coronaviruses which includes important veterinary viruses and the SARS virus.+ssRNA,-ssRNA,dsRNAprotein interacting with a key part ofRNA World hypothesisLine
7、ar ds DNA genomes that are replicated in the nucleusHepatitis C virus.Functions of virion proteinsRhabdoviridae(rabies virus）Triangulation number,TVirion structure and functionEnveloped virions of RNA viruses with ssRNA genomes with helical capsidsPrinciples of building virions:Symmetry is key1956:p
8、ointed out that most virus particles were spherical or rod-shaped in the EMRegulation and timing of the replication cyclestudy improves our understanding ofSpecific recognition and packaging of the nucleic acid genomeRNA can only be made from a dsDNA template,Created by symmetrical arrangement of ma
9、ny identical proteins to provide maximal contact and non-covalent bondingthe human cellular machinery.develop a 3D picture of a herpes virusds DNA genomes that are replicated in the cytoplasmssDNA genomesA basic problem with a ssDNA genome:RNA can only be made from a dsDNA template,ssDNA must be con
10、verted into dsDNA before mRNA is made DNA synthesis must precede mRNA productionLinear ss DNA genomes that are replicated in the nucleusRNA genomes Cells have NO RNA-dependent RNA polymerases(RdRp)to replicate the genomes of RNA viruses,or to make mRNA from RNA RNA virus genomes encode novel RdRp Po
11、lymerases produce both RNA genomes and mRNA from RNA templates+ssRNA,-ssRNA,dsRNA+ssRNA Hepatitis A virus,foot and mouth disease virus,and rhinoviruses which cause the common cold.The coronaviruses which includes important veterinary viruses and the SARS virus.Hepatitis C virus.Yellow fever virus.Po
12、sitive-strand RNA viruses that make no subgenomic mRNAsPositive-strand RNA viruses that make one or more subgenomic mRNAs-ssRNA RdRp Reassortment:Influenza virusNegative-strand RNA virusessDNA must be converted into dsDNA before mRNA is madeRNA can only be made from a dsDNA template,Cellular compone
13、nts:Binding to host cell receptorsThe viral nucleic acid genome carries the information needed to replicate,build,and spread virions in the world.develop a 3D picture of a herpes virusNo genes encoding the complete protein synthesis machineryOrthomyxoviridae(influenza virus)Hershey-Chose experimentT
14、he coronaviruses which includes important veterinary viruses and the SARS virus.Viruses are molecular machines that play active role in delivery of genomeInteraction with cell components to direct transport of genome to the appropriate sitEnveloped virions of RNA viruses with ssRNA genomes with heli
15、cal capsidsAn infectious virion is a molecular machineCellular components:Reassortment:Influenza virusHepadnavirusesNMR spectroscopy for the first time toCryo-electron microscopyAcquisition of the lipid envelopeAmbisense RNA viruseDouble-stranded RNA(dsRNA)Many dsRNA genomes are segmented dsRNA cann
16、ot be translated by ribosomesds RNA virusesRetrovirus HIV HTLV Integrate into the host DNA HBVRetrovirusesHepadnavirusesStructure Nanometer:10-9 meters Atom:0.2-0.3 nm diameter Alpha helix in protein:1 nm diameter DNA:2 nm diameter Ribosome:20 nm diameter Poliovirus:30 nm Mimivirus:750 nmDNA:2 nm di
17、ameterDouble-stranded RNA(dsRNA)Regulation and timing of the replication cycleTriangulation number,TDelivery of the genome+ssRNA,-ssRNA,dsRNAReassortment:Influenza virusNo classical centromeres or telomeres found in standard host chromosomesWith cell components to ensure efficient infectious cycleTh
18、ey provide rules for“self-assembly”Protection of the genomeNOT all(+)RNA is mRNAHow can you make a round capsid from proteins with irregular shapes?3 nm diameterRNA World hypothesisRule 2:These bonding contacts are usually non-covalentds RNA,+ss RNA,-ssRNA,RetroOrthomyxoviridae(influenza virus)Each
19、virus family has its own characteristic genome strategyDNA synthesis must precede mRNA productionFunctions of virion proteins Protection of the genome Assembly of a stable,protective protein shell Specific recognition and packaging of the nucleic acid genome Interaction with host cell membranes to f
20、orm the envelope Delivery of the genome Binding to host cell receptors Transmission of signals that induce uncoating of the genome Induction of fusion with host cell membranes Interaction with cell components to direct transport of genome to the appropriate sit Other interactions with host With cell
21、 components to ensure efficient infectious cycle With cell components for transport to sites of assembly With the host immune systemVirus particles are not inert structures Virions are metastable structures:have not attainted minimum free energy conformation Gained only when an unfavorable energy ba
22、rrier is surmounted,following irreversible conformational changes during attachment and entry Viruses are molecular machines that play active role in delivery of genome To be infectious,the particles must be metastable Must protect the genome(stable)Must come apart quickly on infection(unstable)An i
23、nfectious virion is a molecular machine Has moving parts and does workVirion structure and function Structure(the particles;the virion)Created by symmetrical arrangement of many identical proteins to provide maximal contact and non-covalent bonding Function(genome delivery)Made possible because the
24、structure is Not permanently bonded together Can be taken apart or loosened on infection to releaseThe tools of viral structural biology Electron microscopy X-ray crystallography Cryo-electron microscopy Nuclear magnetic resonance spectroscopy(NMR)TITLE:Artificial Nano“T4 Bacteriophage”Description:“
25、T4 Bacteriophage”is a virus like the robot in the living body.Artificial nano“T4 Bacteriophage”was fabricated by FIB-CVD on Si surface.Size of the artificial nano“T4 Bacteriophage”is about ten times as large as the real virus.It is made of Diamond-like Carbon.It is likely to begin to walk in the nan
26、o space!Magnification:25,000XInstrument:SII NanoTechnology Inc./SMI2050MS2Submitted by:Reo Kometani&Shinji Matsui(University of Hyogo)Structure of Reovirus Core Determined Via X-ray CrystallographyEnveloped viruses and coated vesicles cryo-electron microscopy and tomography+ssRNA,-ssRNA,dsRNAElectro
27、n microscopyMust come apart quickly on infection(unstable)ds RNA,+ss RNA,-ssRNA,RetroVirions are metastable structures:have not attainted minimum free energy conformationds DNA genomes that are replicated in the cytoplasmWith cell components to ensure efficient infectious cycleprotein interacting wi
28、th a key part ofDelivery of the genomeMust come apart quickly on infection(unstable)human cellular protein(white)Positive-strand RNA viruses that make one or more subgenomic mRNAsRhabdoviridae(rabies virus）The Baltimore SystemNegative-strand RNA viruseThey provide rules for“self-assembly”human cellu
29、lar protein(white)Reassortment:Influenza virusViral proteins have structural properties that permit regular and repetitive interactions among themWith cell components to ensure efficient infectious cycleHerpes virus protein(red)docks with human cellular protein(white)UK scientists have used solution
30、-state NMR spectroscopy for the first time to develop a 3D picture of a herpes virus protein interacting with a key part of the human cellular machinery.The study improves our understanding of how the virus hijacks human cells and could eventually lead to new targets for drug therapy.Principles of b
31、uilding virions:Symmetry is keyWatson and Crick did more than discover DNA structure1956:pointed out that most virus particles were spherical or rod-shaped in the EMKnew particles were made with many copies of few proteins(genetic economy)Viral proteins have structural properties that permit regular
32、 and repetitive interactions among themThey provide rules for“self-assembly”Rule 1:Each subunit has“identical”bonding contacts with its neighbors Rule 2:These bonding contacts are usually non-covalent Many capsid proteins can self assemble into“virus-like particles”(VLPs)The HBV and HPV vaccines are
33、 VLPs made in yeastHelical symmetryEnveloped virions of RNA viruses with ssRNA genomes with helical capsids Paramyxoviridae(measles virus)Rhabdoviridae(rabies virus）Orthomyxoviridae(influenza virus)Filoviridae(Ebola virus)How can you make a round capsid from proteins with irregular shapes?Clue1:All
34、round capsids have precise numbers of proteins;multiples of 60 are common(60,180,240,960)(T number)Clue 2:Spherical viruses come in many size,but capsid proteins are 20-60 kDa averageBinding to host cell receptorsOrthomyxoviridae(influenza virus)Cryo-electron microscopyHepadnavirusesFraenkel-Conrats
35、 work with TMVIntegrate into the host DNACryo-electron microscopyTriangulation number,TCellular components:Viral proteins have structural properties that permit regular and repetitive interactions among themMust protect the genome(stable)ds RNA,+ss RNA,-ssRNA,RetroQuasiequivalenceFunction(genome del
36、ivery)The HBV and HPV vaccines are VLPs made in yeastPrinciples of building virions:Symmetry is keyPositive-strand RNA viruses that make no subgenomic mRNAsInteraction with host cell membranes to form the envelopeThe viral nucleic acid genome carries the information needed to replicate,build,and spr
37、ead virions in the world.With cell components for transport to sites of assemblyTriangulation number,TQuasiequivalenceStructurally complex capsidsCapsid can be covered by host membranes:enveloped virions Enveloped virions are common,particularly those that infect animals Envelope is lipid bilayer de
38、rived from host cell Envelope acquired by budding of nucleocapsid through a cellular membraneAssembly of helical nucleocapsidsAssembly of isometric nucleocapsidsAcquisition of the lipid envelopeOther virion components Enzymes Polymerases,integrases,proteases Activators,mRNA degradation,required for
39、efficient infection,mRNA Cellular components:Histones,tRNAs,myristate,lipid VIPERdbds RNA,+ss RNA,-ssRNA,RetroPositive-strand RNA viruses that make one or more subgenomic mRNAsDouble-stranded RNA(dsRNA)Many dsRNA genomes are segmented dsRNA cannot be translated by ribosomes Other interactions with h
40、ost With cell components to ensure efficient infectious cycle With cell components for transport to sites of assembly With the host immune systemPrinciples of building virions:Symmetry is keyWatson and Crick did more than discover DNA structure1956:pointed out that most virus particles were spherica
41、l or rod-shaped in the EMKnew particles were made with many copies of few proteins(genetic economy)Viral proteins have structural properties that permit regular and repetitive interactions among themds RNA,+ss RNA,-ssRNA,Retrods RNA,+ss RNA,-ssRNA,RetroDNA:2 nm diameterCellular components:Enveloped
42、virions of RNA viruses with ssRNA genomes with helical capsidsReassortment:Influenza virusdevelop a 3D picture of a herpes virusThey provide rules for“self-assembly”The viral nucleic acid genome carries the information needed to replicate,build,and spread virions in the world.Helical symmetryThe cor
43、onaviruses which includes important veterinary viruses and the SARS virus.Binding to host cell receptorsTriangulation number,TPrinciples of building virions:Symmetry is keydsRNA cannot be translated by ribosomesBinding to host cell receptorsOrthomyxoviridae(influenza virus)Information Not contained in viral genomesCapsid can be covered by host membranes:enveloped virionsNo genes encoding the complete protein synthesis machinery Many capsid proteins can self assemble into“virus-like particles”(VLPs)The HBV and HPV vaccines are VLPs made in yeast
