Reverse transcription

Ahmed YossreTo Dr. Noha Khalifa

Agenda• Introduction• Function in viruses• The process of reverse transcription• Steps of creating viral DNA• How does Integrase enzyme works ?

IntroductionWhat is Reverse transcription ?

The process of DNA transcription but in the opposite direction by the reverse transcriptase.

It was discovered by Howard Temin & David Baltimore at the University of Wisconsin–Madison.

Function in Viruses

• Viruses uses the enzyme to integrate their viral RNA into the host cell

• Some viruses make thier RNA works as a DNA complementary strand

The process of reverse transcription

• The genomes of retroviruses consists of 2 molecules of single strand RNA with a 5’Cap and 3’polyadenylated tail.

• Ex. Of retroviruses:1. HIV virus2. HTLV virus:

The process of creating a double-stranded viral DNA takes place in the cytosol in a series of steps:

Steps of creating a Viral DNA

• Step I:– The tRNA hybridizes to a complementary part

of the viral genome called “Primary Binding site”

• Step II:– The complementary DNA then binds with the

Non-coding regions and the R region of the viral RNA

Steps of creating a Viral DNA

• Step III:– The RNAse H degrades the 5’ end of the RNA

which removes the non-Coding and R regions.

• Step IV:– The Primer starts synthesizing DNA from the

3’ end of the viral genome and adds it to the R-region of the RNA strand

Steps of creating a Viral DNA

• Step V:– The cDNA is extended and the rest of majority

of the viral RNA is degraded• Step VI:

– After synthesizing the complete strand a new strand is being synthesized from the viral RNA

Steps of creating a Viral DNA

• Step VII:– The Primer Binding Site of the first strand then

jumbs to hybrid to the second Primer Binding Site.

• Step VIII:– Both strands are then incorporated and

integrated with the Integrase enzyme

How does Integrase works ?

• 1st : It binds with the nucleus membrane and open a hole into it .

• 2nd : It takes the new viral DNA and go with it into the nucleus.

• With the help of other enzymes it binds the viral DNA with the DNA.

http://www.youtube.com/watch?v=9leO28ydyfU

References

• Wikipedia #1• Wikipedia #2• Aids.about.com• Bioproductsmd.com• Google.com

Thank YouAhmed Yossre