Tuesday, July 3, 2012

July 3 Lytic Cycle continued






T2 viruses attacking an <em>E-coli</em> bacterium
T2 bacteriophage virus attacking E. coli bacterium

*** diagram handdrawn: ds DNA, ss RNA - sense; ss RNA + sense, ds RNA

Lytic Cycle: Step 3: Synthesis 

Host genome:
Genome of virus:

2 main molecule types that must be produced during synthesis:
--------------------------------------------- and ----------------------------------------------------------
*Drug targets: nucleotide analogue

SEE DNA REVIEW SLIDE POSTED ON BLACKBOARD
Master strand of DNA:
 + sense strand of RNA:
-sense strand of RNA:
---------------------------------------------------------------------------------------------------------
(SEE HANDOUT DONE IN CLASS using “Synthesis stage of viral life cycle” review item, also Fig. 13.13)
[Summarize the Steps of Synthesis for each genome type below]
- ds DNA genome



-ss DNA genome (not covered in class, use text)



- sense (non-sense) ssRNA genome



+ sense ssRNA genome



ds RNA genome (not covered in class, use text)



Lytic Cycle: Step 4: Assembly (Maturation)
*drug target: protease inhibitors
* vital parts are put together
  • capsomeres form capsid
  • genetic
    material in capsid
  • Enzymes in capsid
  • enveloped peplomers go to membrane
*Drug target: protease inhibitors


Lytic Cycle: Step 5: Release(Lysis)
* Cell releases virus particles
Phages: host cell explodes, host cell dies

Naked: host cell explodes
Enveloped:viruses bud out, gain envelope and peplomers


 Fig. 13.14 
AIDS virus budding from a white blood cell

http://www.microbiologyonline.org.uk/about-microbiology/introducing-microbes/viruses 

*** Drug: tamiflu prevents budding so the envelope can't form

Lysogenic Life Cycle  Fig. 13.11
Step 1 -Attachment (same as lytic)
Step 2 -Penetration (same as lytic)

Step 3 - Incorporation:
Viral genes: join host cell genome (integrase)****integrase inhibitors is a drug target***
Incorporated Virus genes is now called: Provirus (or called prophage)
Some known triggers which activate expression of viral genes: 
  • Chemical, physical, emotional trauma, age, hormones, immune system weak, UV radiation, AA arginine, etc.



*drug target: integrase inhibitors
Step 4 – Synthesis
_______________________________________________________________________
[Summarize the Steps of Synthesis for each genome type below]
+ sense ssRNA genome – retrovirus (NOTE: see diagram done in class)  *drug target: reverse transcriptase inhibitors


DNA genome – (not covered in class, use text)


Step 5 - Assembly
Step 6 - Release
*******

Lysogenic Life Cycle
*DNA viruses
*(RNA viruses) Retroviruses
*** draw on diagram***

Animal Virus options: 
Lystic Cycle.... imediate replication with host cell death
Lysogenic cycle (3 options): 
  1. Dormant/latent infection- triggered later
  2. Persistent infection: continous release- cell lives
  3. Tumor formation: oncogene activation
normal and abnormal (potentially cancerous cell)

Viral connection to cancer:
* Cancer is a result of uncontrolled cellular reproduction
* Proto-oncogene (prexisting) gene converted to oncogene by mutation: at least 2 mutations to change
Figure 13.15

http://www.youtube.com/watch?feature=player_embedded&v=U6QwtBl870I


Specific viruses and cancer:

*Example cancer-causing viruses:
  • Human papilloma virus = genital warts and cervical cancer
  • Hepatitis B and C viruses = liver cancer
  • human herpes virus 4= Burkitt's lymphoma (coinfection with malaria) 
  • human Herpes Virus B = Kaposi's sarcoma (coinfection with HIV-1) purple spots that attack connective tissue
Known oncogenes (turned OFF or ON to cause cancerous behavior)
  •  Loss of tumor suppressor genes
    • Normally on- inhibit mitosis in abnormal cells
  • Loss of apoptosis 
    • Normally on - cause abnormal cells to commit suicide
    • Example p53 tumor suppressor.... picture..of development of figure and toes that use apoptosis to divide them, example of child who have two fused fingers instead of seperating
  •  Angiogenesis
    • Normally off - growth of new blood vessels into mass of new cells
    • What is Tumor Angiogenesis? picture: small localized tumor.... angiogenesis causes tumor that can grow and reproduce becuse new blood vessels to bring nutrients
  •  Metastasis
    • normally off- separation and spread of cells

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