Step
2: Reverse Transcription
HIV's genes are carried in two strands of RNA, while the genetic
material of human cells is found in DNA. In order for the virus
to infect the cell, a process called "reverse transcription"
makes a DNA copy of the virus's RNA.
After the binding process, the viral capsid (the inside of the
virus which contains the RNA and important enzymes) is released
into the host cell. A viral enzyme called reverse transcriptase
makes a DNA copy of the RNA. This new DNA is called "proviral
DNA."
Step
3: Integration
The HIV DNA is then carried to the cell's nucleus (center), where
the cell's DNA is kept. Then, another viral enzyme called integrase
hides the proviral DNA into the cell's DNA. Then, when the cell
tries to make new proteins, it can accidentally make new HIVs.
Step
4: Transcription
Once HIV's genetic material is inside the cell's nucleus, it directs
the cell to produce new HIV.
The strands of viral DNA in the nucleus separate, and special
enzymes create a complementary strand of genetic material called
messenger RNA or mRNA (instructions for making new HIV).
Step
5: Translation
The mRNA carries instructions for making new viral proteins from
the nucleus to a kind of workshop in the cell. Each section of
the mRNA corresponds to a protein building block for making a
part of HIV.
As each mRNA strand is processed, a corresponding string of proteins
is made. This process continues until the mRNA strand has been
transformed or "translated" into new viral proteins
needed to make a new virus.
Step
6: Viral Assembly
Finally, a new virus is assembled. Long strings of proteins are
cut up by a viral enzyme called protease into smaller proteins.
These proteins serve a variety of functions; some become structural
elements of new HIV, while others become enzymes, such as reverse
transcriptase.
Once the new viral particles are assembled, they bud off the host
cell, and create a new virus. This virus is then able to infect
new cells. Each infected cell can produce a lot of new viruses.