際際滷

際際滷Share a Scribd company logo

Reverse transcription of hiv 1 ..

Download as PPTX, PDF
A
AvisekChakraborty6

This is my another presentation in this platform. Hope you all can understand clearly through this presentation.

1 of 11
Download to read offline
HIV-1ReverseTranscription PowerPointpresentation By AvisekChakraborty MicrobiologyDepartment 2ndsemester Collegerollno-19MB0028
Abstract:- Reverse transcription and integration are the defining features of the Retroviridae; the common name retrovirus derives from the fact that these viruses use a virally encoded enzyme, reverse transcriptase (RT), to convert their RNA genomes into DNA. Reverse transcription is an essential step in retroviral replication.
The Process of Reverse Transcription:- When a mature HIV-1 virion infects a susceptible target cell, interactions of the envelope glycoprotein with the coreceptors on the surface of the cell brings about a fusion of the membranes of the host cell and the virion . This fusion introduces the contents of the virion into the cytoplasm of the cell, setting the stage for reverse transcription.
Reverse transcription initiates from an RNA primer provided by a specific cellular tRNA (tRNA Lys3). The primer hybridizes to the primer Binding Site (PBS) of the genomic RNA. Reverse transcriptase catalyzes RNA dependent DNA synthesis. Synthesis of the minus-strand DNA generates an RNA-DNA hybrid. Rnase H activity of reverse transcriptase degrades the RNA strand, leaving the nascent minus-strand DNA single stranded. The newly synthesized minus-strand DNA hybridizes with the terminal R-region of the 3 end of the viral RNA ( Called the first jump or minus-strand transfer).
After the nascent DNA hybridizes to R, minus--strand DNA synthesis can continue along the viral RNA. As DNA synthesis proceeds, RNase H degrades the RNA strand.
There is a Purine-rich sequence ( called the polypurine tract or PPT) near the 3 end of the viral RNA which is relatively resistant to RNase H cleavage, and it serves as the primer for plus -- strand DNA synthesis. Plus-strand DNA synthesis proceeds until reverse transcriptase starts to copy the tRNA primer. Once the 3 end of the tRNA has been reverse transcribed , an RNA/DNA hybrid that is a substrate for RNase H is created.
The tRNA associated with the nascent viral DNA is then removed by the RNase H activity. This may facilitate annealing to the PBS complement on the minus-strand DNA, providing the complementarity for the Second jump or Plus-strand transfer. Once this Second transfer happens, both the minus and plus DNA strands are extended until the entire DNA is double stranded and creating a DNA that has the same sequences at both ends (these repeats are called the Long Terminal Repeats or LTRs).
Reverse transcription of hiv 1 ..
Why Left hand LTR and Right hand LTR is necessary ? RNA polymerase that initate transcription with in the Left hand LTR can dislodge transcription factor bound to the Right hand LTR as they passed through that region on the proviral DNA inactivating its ability to initiate for transcription. This is called Promotar occlusion. This concept is supported by the observation that mutation or deletion of the Left hand LTR can lead to the initiation of the transcription in the Right LTR resulting in transcription of the cellular genes downstream of the proviral DNA.
The cellular cleavage and poly adenylation machinery recognizes the highly conserved AAUAAA poly adenylation signal in RNA.
THANK YOU

More Related Content

Reverse transcription of hiv 1 ..

  • 2. Abstract:- Reverse transcription and integration are the defining features of the Retroviridae; the common name retrovirus derives from the fact that these viruses use a virally encoded enzyme, reverse transcriptase (RT), to convert their RNA genomes into DNA. Reverse transcription is an essential step in retroviral replication.
  • 3. The Process of Reverse Transcription:- When a mature HIV-1 virion infects a susceptible target cell, interactions of the envelope glycoprotein with the coreceptors on the surface of the cell brings about a fusion of the membranes of the host cell and the virion . This fusion introduces the contents of the virion into the cytoplasm of the cell, setting the stage for reverse transcription.
  • 4. Reverse transcription initiates from an RNA primer provided by a specific cellular tRNA (tRNA Lys3). The primer hybridizes to the primer Binding Site (PBS) of the genomic RNA. Reverse transcriptase catalyzes RNA dependent DNA synthesis. Synthesis of the minus-strand DNA generates an RNA-DNA hybrid. Rnase H activity of reverse transcriptase degrades the RNA strand, leaving the nascent minus-strand DNA single stranded. The newly synthesized minus-strand DNA hybridizes with the terminal R-region of the 3 end of the viral RNA ( Called the first jump or minus-strand transfer).
  • 5. After the nascent DNA hybridizes to R, minus--strand DNA synthesis can continue along the viral RNA. As DNA synthesis proceeds, RNase H degrades the RNA strand.
  • 6. There is a Purine-rich sequence ( called the polypurine tract or PPT) near the 3 end of the viral RNA which is relatively resistant to RNase H cleavage, and it serves as the primer for plus -- strand DNA synthesis. Plus-strand DNA synthesis proceeds until reverse transcriptase starts to copy the tRNA primer. Once the 3 end of the tRNA has been reverse transcribed , an RNA/DNA hybrid that is a substrate for RNase H is created.
  • 7. The tRNA associated with the nascent viral DNA is then removed by the RNase H activity. This may facilitate annealing to the PBS complement on the minus-strand DNA, providing the complementarity for the Second jump or Plus-strand transfer. Once this Second transfer happens, both the minus and plus DNA strands are extended until the entire DNA is double stranded and creating a DNA that has the same sequences at both ends (these repeats are called the Long Terminal Repeats or LTRs).
  • 9. Why Left hand LTR and Right hand LTR is necessary ? RNA polymerase that initate transcription with in the Left hand LTR can dislodge transcription factor bound to the Right hand LTR as they passed through that region on the proviral DNA inactivating its ability to initiate for transcription. This is called Promotar occlusion. This concept is supported by the observation that mutation or deletion of the Left hand LTR can lead to the initiation of the transcription in the Right LTR resulting in transcription of the cellular genes downstream of the proviral DNA.
  • 10. The cellular cleavage and poly adenylation machinery recognizes the highly conserved AAUAAA poly adenylation signal in RNA.