July 3 Lytic Cycle continued

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 


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***

http://www.youtube.com/watch?v=wLoslN6d3Ec

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