Virology Introduction MMG413
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Ana Karla de Lima
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This 4 page Class Notes was uploaded by Ana Karla de Lima on Saturday February 7, 2015. The Class Notes belongs to MMG413 at Michigan State University taught by Michele M Fluck in Fall. Since its upload, it has received 128 views. For similar materials see Virology in Microbiology at Michigan State University.
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Date Created: 02/07/15
Virology Notes Introduction Viruses are parasites of cells They have evolved by making use of cellular processes from human or animal cells There are 8 classes and the determinant used to generate these 8 classes is the viral genome 1 Genome dependent Organization of viruses I DsDNA Polyomavirus Papilomavirus adenovirus SsDNA Parvovirus gt Non enveloped Y Small DNA viruses I DsDNA HSV Herpes B Vaccinia virus Cowpox gt Enveloped I Y Large DsDNA two families Herpes and Poxviridae Retrovirus GOES TO NUCLEUS 2 classes HIV and HBV Authentic retrovirus convert its RNA genome to dsDNA and quotPseudoquot retro Converts its partially ssDNA to fully dsDNA Eg Herpes family divided into 3 subfamilies alpha HHV3human herpes virusvaricelIazoster beta human cytomegalovirus and gamma Epstein Bar virusHHV4 and KaposisarcomaHHV8 these 3 genomes are similar but it differs by their length and by the presence or absence of end repeats andor internal repeat Eg2 Polyomavirus 3 different genomes skin cancer brain degeneration kidney problem gt the genomes look similar but infect dif Cells and cause dif Diseases Eg3 Papillomavirus can infect genitals and some other epithelial cells gt 60 welldefined strains with very different properties with respect to induction of cervical carcinoma just 3 or 4 have the armfu capacity 11 The DNA Classes SsDNA gt Parvovirus DsDNA circular gt Polyoma DsDNA linear gt Adeno DsDNA circle gapped gt Hepadna DsDNA linear gt Herpes inside the cells has the possibility to became circular extragenetic material to make all the glycoproteins DsDNA linear X linked gt Pox needs a lot more of genetic material because doesn t use the host polymerase strand RNA produce one mRNA strand RNA with multiple mRNAs strand 3 5 multiple RNA segments ambisense dsRNA segmented genome gt ALL RNA VIRUS ARE CYTOPLASMIC EXCEPTION INFLUENZA SEGMENTED STRAND RNA examples Poliovirus cold virusesrhinoviruses gt they go to the cytoplasm gt translation So then next step after it arrives in the cytoplasm is the translation Close to the 5 PPP prime end will be a signaling sequence AUG examples ebola rhabies Before it can be translated it needs to become a strand RNA 2 types of H strand RNA Segmented genome influenza each segment of the genome encode a protein gt DsRNA segmented examples Reovirus and Rotavirus diarrhea in infants Ambisense and strand in the same RNA Examples Lymphochoriomeningitis LCMV 12 The RNA Classes DsRNA segmented Reo ssRNA Picoma ssRNA FlaviTogacorona ssRNArhabdo ssRNA segmented Orthomyxo ssRNA Paramyxo Most mammalian RNA viruses have an envelope except for picornaviruses strand and reorota dsRNA Naked viruses have better environmental resistance Very large genomes are found only among DNA viruses 2 Transcription rules The first step for a DsDNA virus genome circular or linear after migration into the nucleus is transcription which is all mediated by the host DNA machine Parvoviruses are ssDNA but when they arrive to the nucleus they will be converted in DsDNA HBV has dsssDNA in one unique virus and because of it it will need to be convert to fully dsDNA All retroviruses after reverse transcribing ssRNA will become dsDNA The transcription rules are based upon the rules of the host cell TATA sequence box the core promoter sequence tells where the transcription need to be initiated Specific sequence upstream of TATA 3 Viral Rules All encode at least one viral structural proteins glycoprotein or normal protein Herpes many proteins Most encode some proteinsenzymes involved in at least one of aspect of transcription translation and genome replication A produce one or more mRNA 31 DNA Transcription Rules Similar to the host genome contains genes regulated by cisacting sequences TATA box gt TATA Binding Protein TBP Diverse specific sequences located upstream of TATA gt Recruit cell protein with similar DNA specific binding TATA initiation of transcription bound by TBP cell protein Recruits the polymerase host DNA Dependent RNA polymerase POL In RNA Viruses we will have the RNA dependent RNA polymerase Note You can get transcription without the upstream sequences but it s very inefficient Basal transcription low levels of transcription The box are needed for bring factors that can enhance transcription inducing high levels of transcription andor eg HBV it has a binding site for a transcription factor that just exists in the liver cells andor cell there re factors that control the cell cycle and some of the DNA viruses are extreme dependent of it If the cell is resting they won t do anything Factors that binding the upstream sequences they free the DNA from histones so then the polymerase can go AP1 gt Cell cycle NFKB gt HIV through There s an HIV protein that interacts with one of the factors TFII complex which helps the phosphorylation of POL II and escape from the promoter gt iniciation of transcription The dsDNA viruses Polyoma HPV Adenovirus and herpes the ssDNA when they become ds and HIV use the upstream sequences There re 4 viral classes that use common host process 2 dSDDNN All of them end up in a dsDNA genome after 35 d d DNA conversion Therefore once it s a dsDNA C39 appe S genome it will go similar to the host d Retrowrus process AFTER TRANSCRIPTION gt REPLICATION OF THE GENOME gt Small viruses as Polyoma papilloma and parvovirus are very deoendt on host proteins including the host DNA polymerase because they don t have so much genetic information They use one viral protein which binds a viral sequence called the Origin gtMedium large viruses as adenovirus and herpes this one is totally independent of host in fact can replicate in the cytoplasm encode their own DNA dependent DNA polymerase The HIV intregates to the host DNA and produces mRNA some of these mRNA unslipiced will serve as the virus genome the new template to make another virus The PoxVaccinia goes to the cytoplasm and because of it has its own DNA polymerase gt totally independent of the cell for transcription and replication QUESTION What could be a major difference btw DNA and RNA genomes Where the RNA genome replicates cytoplasm exception influenza what protein they use RNA dep RNA poly all RNA viruses have to make their own RNA poly because the cell doesn t have this 0 RNA VIRUSES TRANSLATION be translated This problem is solved it packaging a RNA depend RNA polymerase inside the virion They must copy RNA first Ds RNA they re in segments For the first round they need to make an mRNA for this ds genome so they bring the polymerase in the virion that copy the parental RNA in the virion Question Which viruses use the host TBP protein Small DNA viruses all the DNA viruses except POX need this The retrovirus too The H strand RNA viruses need to do the RNA dep RNA polymerase to put inside the virion Question Are there other virus that carry a viral polymerase in the virion strand RNA dsRNA retroviruses Pox DNA dep RNA polymerase DNA GENOME ds small gt use host DNA pol ds mediumlarge gt viral DNA pol ENCODES ds Large non nuclear ENCODE THE POL an it s in the virion ss small Polyoma Papilloma Adeno amp Herpes Pox Pa rvo gapped DNApseudovirus Hepatitis B HBV HIV amp All retroviruses RETROVIRUSES ssRNA with DNA intermediate RNA GENOME ds RNA Rota amp Reo ss strand RNA asingle genomic RNA b subgenomic mRNAs Polio Rhino ss strand RNA nonsegmented Toga amp Corona cbola amp Rabies Segmente genome Influenza The RNA from the RNA viruses are either a mRNA and a rep intermediate VIRUSES THAT ENCODE A POLYMERASE All RNA viruses retroviruses reverse transcriptase RNA dep polDNA dep DNA pol Adeno amp herpes mediumlarger nuclear DNA viruses POX DNADNA POL and DNARNA pol
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