《微生物学 Microbiology》课程PPT教学课件（英文版）viruses viroids and prions 2/2

Chapter 13,part B Viruses,Viroids,and Prions

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings B.E Pruitt & Jane J. Stein Chapter 13, part B Viruses, Viroids, and Prions

Attachment.Penetration. and Uncoating Plasma membrane Vesicle of host cell (a)Attachment (b)Endocytosis (c)Penetration (d)Uncoating Figure 13.14

Attachment, Penetration, and Uncoating Figure 13.14

Release of an enveloped virus by budding Viral capsid Host cell plasma membrane Viral protein Bud Bud Envelope (a)Release by budding (b)Alphavirus Figure 13.20

Release of an enveloped virus by budding Figure 13.20

Multiplication of DNA Virus Papovavirus Virion attaches to host cell ⑦Virions are released Host cell DNA Capsid DNA 2 Virion penetrates ⑥Virions mature cell and its DNA is Cytoplasm uncoated Capsid proteins mRNA ⑤Late translation: capsid proteins are synthesized 4 3 Early transcription and Late transcription; DNA is replicated translation;enzymes are synthesized Figure 13.15

Multiplication of DNA Virus Figure 13.15 Virion attaches to host cell Virion penetrates cell and its DNA is uncoated Early transcription and translation; enzymes are synthesized 1 2 3 DNA Late transcription; DNA is replicated 4 Late translation; capsid proteins are synthesized 5 6 Virions mature Capsid Papovavirus Host cell DNA Cytoplasm 7 Virions are released Capsid proteins mRNA

Pathways of Multiplication for RNA-Containing Viruses Attachment Capsid、 Nucleus RNA Host -Cytoplasm cell Maturation Penetration and Release and Uncoating Translation and Synthesis RNA Rep lication of Viral Proteins Viral- (a): strand mRNA is ed m the The+strand(mRNA)must firs strand. be transcribed from the-viral ore proteins can tein into capsid om mN Key: dsRNA that is incorporated as new viral genome. Viral genome 厂+or sense strand of viral genome -or antisense strand of viral genome Capsid proteins mRNA is produced inside the ss single-stranded and RNA- and ds=double-stranded NApoiymerase Figure 13.17

Pathways of Multiplication for RNA-Containing Viruses Figure 13.17

Multiplication of a Retrovirus Reverse Capsid transcriptase DNA Virus Two identical stands of RNA Retrovirus penetrates Host host cell. cell DNA of one of the host ⑤Mature cell's chromosomes retrovirus leaves host Reverse cell,acquiring transcriptase an envelope as it buds out. Identical Viral RNA Virion penetrates cell and its DNA is strands of RNA uncoated 4 Transcription of the provirus may also occur, Viral proteins producing RNAfor new retrovirus genomes and RNA that codes for the RN retrovirus capsid and envelope proteins. 3The new viral DNAis tranported into the host cell's nucleus and integrated as a provirus.The provirus may divide indefinitely with the Provirus host cell DNA. Figure 13.19

Multiplication of a Retrovirus Figure 13.19 Retrovirus penetrates host cell. Virion penetrates cell and its DNA is uncoated The new viral DNA is tranported into the host cell’s nucleus and integrated as a provirus. The provirus may divide indefinitely with the host cell DNA. 1 2 3 DNA Transcription of the provirus may also occur, producing RNA for new retrovirus genomes and RNA that codes for the retrovirus capsid and envelope proteins. 4 Mature retrovirus leaves host cell, acquiring an envelope as it buds out. 5 Reverse Capsid transcriptase Virus Two identical + stands of RNA DNA of one of the host cell’s chromosomes Provirus Host cell Reverse transcriptase Viral RNA RNA Viral proteins Identical strands of RNA

Cancer Activated oncogenes transform normal cells into cancerous cells. Transformed cells have increased growth,loss of contact inhibition,tumor specific transplant and T antigens. The genetic material of oncogenic viruses becomes integrated into the host cell's DNA

• Activated oncogenes transform normal cells into cancerous cells. • Transformed cells have increased growth, loss of contact inhibition, tumor specific transplant and T antigens. • The genetic material of oncogenic viruses becomes integrated into the host cell's DNA. Cancer

Oncogenic Viruses Oncogenic DNA Viruses Oncogenic RNA viruses 。Adenoviridae 。Retroviridae ·Heresviridae 。Viral RNA is 。Poxviridae transcribed to DNA which can integrate 。Papovaviridae into host DNA 。Hepadnaviridae ·HTLV1 。HTLV2

• Oncogenic DNA Viruses • Adenoviridae • Heresviridae • Poxviridae • Papovaviridae • Hepadnaviridae Oncogenic Viruses • Oncogenic RNA viruses • Retroviridae • Viral RNA is transcribed to DNA which can integrate into host DNA • HTLV 1 • HTLV 2

Latent Viral Infections Virus remains in asymptomatic host cell for long periods ·Cold sores,shingles Persistent Viral Infections Disease processes occurs over a long period, generally fatal Subacute sclerosing panencephalitis (measles virus)

• Latent Viral Infections • Virus remains in asymptomatic host cell for long periods • Cold sores, shingles • Persistent Viral Infections • Disease processes occurs over a long period, generally fatal • Subacute sclerosing panencephalitis (measles virus)

Prions 。Infectious proteins Inherited and transmissible by ingestion,transplant, surgical instruments 。 Spongiform encephalopathies:Sheep scrapie, Creutzfeldt-Jakob disease,Gerstmann-Straussler- Scheinker syndrome,fatal familial insomnia,mad cow disease PrPC,normal cellular prion protein,on cell surface PrPsc,scrapie protein,accumulate in brain cells forming plaques

• Infectious proteins • Inherited and transmissible by ingestion, transplant, & surgical instruments • Spongiform encephalopathies: Sheep scrapie, Creutzfeldt-Jakob disease, Gerstmann-Sträussler￾Scheinker syndrome, fatal familial insomnia, mad cow disease • PrPC, normal cellular prion protein, on cell surface • PrPSc, scrapie protein, accumulate in brain cells forming plaques Prions