Chapter 25: Retroviruses and Reverse Transcribing Viruses

retroviruses are

Positive-Strand Viruses That Use Reverse Transcriptase in Their Life Cycles

reverse transcriptase

enzyme that converts ssRNA into dsDNA

retrovirus examples

• HIV

• Lentivirus

HIV

• retrovirus

• Cause of acquired immunodeficiency syndrome (AIDS)

• Two copies of RNA genome.

• has Reverse transcriptase and integrase.

Lentivirus

• retrovirus

• AKA HIV-1 and HIV-2

• most common cause of AIDS in US (HIV-1)

• HIV-2 = common in developing nations

roles of reverse transcriptase in HIV infection

• RNA-dependent RNA polymerase

• DNA-dependent DNA polymerase

• Ribonuclease

HIV life cycle

• HIV glycoproteins bind to receptors on the host cell

• HIV fuses into host cell and dumps its RNA

• reverse transcriptase turns RNA into dsDNA

• integrase integrates viral DNA into host DNA

• replication of hybrid DNA and formation of new RNA

• new RNA assembled into new HIV molecule

• budding of HIV molecule until it pops out of the host cell

• protease matures the HIV by cutting proteins/RNA

hepatitis B

• reverse transcribing virus

• smallest DNA virus

• spread through body fluids and syringes

• targets liver

hepatitis b life cycle

• made of one complete negative DNA strand and a complementary +DNA strand with a gap

  • partial dsDNA

• viral polymerase p bound to genome

• host enzymes repair partial dsDNA and convert viral genome into closed circular DNA

• genome transcribed by host RNA polymerase and mRNA formed