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Reverse Transcriptase
(RNA-dependent DNA Polymerase)
Crystallographic structure of reverse transcriptase
RNA dependent DNA Polymerase
In the fields of molecular biology and biochemistry,
a reverse transcriptase, also known as RNA
dependent DNA polymerase, is a DNA
polymerase enzyme that transcribes single
stranded RNA into double-stranded DNA. It also
helps in the formation of a double helix DNA once
the RNA has been reverse transcribed into a
single strand cDNA. Normal transcription involves
the synthesis of RNA from DNA; hence, reverse
transcription is the reverse of this.
Functions in virus
The enzyme is encoded and used by reverse-transcribing
viruses, which use the enzyme during the process of
replication. Reverse-transcribing RNA viruses, such as
retroviruses, use the enzyme to reverse-transcribe their
RNA genomes into DNA, which is then integrated into the
host genome and replicated along with it.
HIV infects humans with the use of this enzyme. Without
reverse transcriptase, the viral genome would not be able
to incorporate into the host cell, resulting in the failure of
the ability to replicate.
Process of Replication
Reverse transcriptase creates single
stranded DNA from an RNA template.
The process of reverse transcription is
extremely error-prone and it is during this
step that mutations may occur. Such
mutations may cause drug resistance
Antiviral Drugs
As HIV uses reverse transcriptase to copy
its genetic material and generate new
viruses (part of a retrovirus proliferation
circle), specific drugs have been designed to
disrupt the process and thereby suppress its
growth. Collectively, these drugs are known
as reverse transcriptase inhibitors.
Applications of Reserve transcriptase
in Molecular Biology
Reverse transcriptase is commonly used in research to apply the polymerase
chain reaction technique to RNA in a technique called reverse transcription
polymerase chain reaction (RT-PCR). The classical PCR technique can be
applied only to DNA strands, but, with the help of reverse transcriptase, RNA
can be transcribed into DNA, thus making PCR analysis of RNA molecules
possible. Reverse transcriptase is used also to create cDNA libraries from
mRNA. The commercial availability of reverse transcriptase allows scientists to
clone, sequence, and characterize DNA.
Reverse transcriptase has also been employed in insulin production. By
Inserting eukaryotic mRNA for insulin production along with reverse
transcriptase into bacteria, the mRNA can insert itself into the bacteria’s
genome, and large amounts of insulin can be created, decreasing the need to
harvest pig pancreas and other such traditional sources. Inserting eukaryotic
DNA (instead of mRNA) into Bacteria would not work because it is fragmented,
with introns, and would not transcribe successfully using the bacteria's
ribosome.
QUIZ
1) What is a reverse transcriptase?
a)
b)
c)
d)
a DNA dependent polymerase
a RNA –dependent DNA Polymerase
a RNA dependent Polymerase
a virus reverse the transcription process
QUIZ
2) A reverse transcriptase is a (an)
a)
b)
c)
d)
protein
virus
nucleic acid
fatty acid
QUIZ
3) A reverse transcriptase has how many
subunits?
a)
b)
c)
d)
one
two
three
four
QUIZ
4) The function of the reverse transcriptase is to
a) to transcribe complimentary strand DNA into RNA
b) to cleave the double strand DNA into single strand
DNA
c) to transcribe single strand RNA into double stranded
DNA
d) to make copies of more single strand RNA
QUIZ
5) The reverse transcriptase is used during
the process of:
a)
b)
c)
d)
replication
translation
transcription
cell division
Challenge Question
If you are a scientist and want to develop a
drug to inhibit viral infection, what do you
need to know to accomplish this mission?
Answers
1) b
2) a
3) b
4) c
5) c
Answer to Challenge Question
Answer may vary between students. The
main idea is that students need to
understand the pathway how the virus infect
the host cell, what enzymes are required in
the process and what drugs can be
developed to prevent the enzymes
formation, thus prevent the lifecycle of the
virus to continue.