Viruses Using Reverse Transcriptase PDF

10.11 Viruses That Use Reverse Transcriptase Retroviruses (RNA viruses; Class VI) and hepadnaviruses (DNA viruses; Class VII) use reverse transcriptase for replication. _ Retroviruses: integration of viral genes into the host genome enveloped virions that contain two identical copie...

10.11 Viruses That Use Reverse Transcriptase Retroviruses (RNA viruses; Class VI) and hepadnaviruses (DNA viruses; Class VII) use reverse transcriptase for replication. _ Retroviruses: integration of viral genes into the host genome enveloped virions that contain two identical copies of the RNA genome Virion contains several enzymes, including reverse transcriptase, and viral tRNA. ^ Retroviral genome is not used as mRNA; converted to DNA by reverse transcriptase and integrated into genome. mRNAs are transcribed from viral DNA by host RNA polymerase  10.11 Viruses That Use Reverse Transcriptase Retroviruses: integration of viral genes into the host genome reverse transcriptase e reverse transcription: synthesize DNA from RNA template (Figure 「 10.23) ( Ribonuclease activity degrades RNA strand of RNA: DNA hybrid. DNA polymerase to make dsDNA from ssDNA Viral tRNA serves as primer. Aling with ^ The gag encodes several small viral structural proteins. nexf slikle figure dsDNA with long terminal repeats forms; repeats assist in integration into genome.  θ Alternative presentation LTR LTR Correction + tRNA primer binding site (PB)  Retroviruses: induction to form new retrovirus virions Retroviral DNA becomes permanent part of host chromosome. Genes may be expressed or remain latent indefinitely. If induced, retroviral DNA is transcribed; RNA can be packaged into virions or translated. (Figure 10.24) Gene expression and protein processing are complex. (Figure 9.22) All retroviruses have the three genes The gag encodes several small viral structural proteins. 、 The pol is translated into a large polyprotein. _ _ _ The env is processed into two distinct envelope proteins. _ 、 Assembly occurs in cytoplasm; virions released by budding.  Hepatitis B virus Hepadnaviruses include hepatitis B (Figure 10.25a) unusual tiny, partially double-stranded genomes overlapping genes Hepadnaviral reverse transcriptase also functions as protein primer for DNA synthesis. Viral replication occurs through an RNA intermediate. a reverse transcriptase https://www.mdpi.com/2076-0817/8/2/63/htm  HBV infection - not retrovirus nucleocapsid enters host nucleus partial genomic DNA strand is completed to form dsDNA. reverse transcriptase synthesizes genomic DNA from RNA template successtal bo so compcated. ㅜ pevsiglent https://pubmed.ncbi.nlm.nih.gov/26776362/  HBV disease impact Chronic infection by Hepatitis B Virus (HBV) Recombinant HBsAg (SHB) ∞ is a global public health problem which ~ as the vaccine affects 250 million people worldwide. Cause acute hepatitis episodes, liver cirrhosis, liver failure and hepatocellular cancer visk carcinoma (HCC) a The viral DNAs are transformed into fully double-stranded covalently closed circular DNA (cccDNA), which initiates RNA Merck has transferred the entire transcription. Episomal cccDNAs can persist technology for HBV vaccine in cells for years which causes chronic production to China in 1993 infection. A great example of Vaccination programs launched since 1980s Sino-American Partnership have been extremely helpful, but the control of HBV infections remains a challenge Further reading: https://quod.lib.umich.edu/c/cohenaids/5571095. because of millions (one-third reside in 0591.013?rgn=main;view=fulltext China) of already chronically infected people https://www.medsci.cn/article/show_article.do?id =169518283046 and incomplete vaccination coverage. w거 Δ  10.16 Prions Infectious proteins whose extracellular form contains no nucleic acid known to cause disease in animals (transmissible spongiform encephalopathies), such as scrapie, bovine spongiform encephalopathy/mad cow, chronic wasting disease, kuru, and Creutzfeldt-Jakob disease All affecting brain ??? scrapie mad cow disease https://www.foodsafetynews.com/2017/07/eu-scientists-investigate-origin-of-isolated-bse-cases/  Prion proteins and the prion infection cycle Host cell contains gene (Prnp) that encodes native form of prion protein (PrPC; prion protein cellular) that is found in neurons/brains of healthy animals. (Figure 10.33a) PrPSc (prion protein scrapie) is pathogenic form with different conformation. Prion proteins are similar but not identical in amino acid sequence. Host range is linked to sequence. PrPSc promotes conversion of PrPC into pathogenic form. Accumulation and aggregation form insoluble amyloids. destroys brain and other nervous tissue Other amyloid diseases include Alzheimer’s, Huntington’s, Parkinson’s, type 2 diabetes—may or may not be prion diseases.  10.33a: Section through brain tissue of a human with variant Creutzfeldt–Jakob disease. Note the spongy nature of the tissue (clearings, arrow) where neural tissue has been lost. Propagation of misfolding and aggregation among the proteins Prion protein gene is encoded by the genome and normal protein is expressed from the genome Pathogenic form (misfolded protein) of the protein promotes conversion of normal protein (properly folded) into the misfolded pathogenic form. Figure 10.33  frperties lptoteins " ' Iike alr : " prion D Payattertia to ^ tendency to aggregate Nonpathogenic prions _ Some fungi have “prions” that do not cause disease and ~ instead adapt to environmental conditions (e.g., altered nutrient utilization, antibiotic resistance, biofilm formation). Example: URE3 normally represses nitrogen-metabolism genes; URE3 prion allows nitrogen sources to be metabolized. Example: MAVS aggregation in humans triggers interferon 1 production in response to viruses. wilk be mentloned in immunity