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-SträusslerScheinker 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