If the provirus was not formed yet, can the virus make viral enzymes?

(I know that it already has some, but supposing it doesn't)

  • $\begingroup$ "...but supposing it doesn't.." What you mean is: it would be feasible for the virus only to translate (in cytosol) the reverse transkriptase, then transcribe "all" from the DNA ("provirus"). And if so, would "making (any other) enzymes" from RNA, not DNA, be contradictory to such rule? This seems a "hidden" no win question... $\endgroup$ Commented May 20, 2021 at 16:59

1 Answer 1


I am afraid your question is really not clear. You are asking one thing in the title of your question, another in the question body and a third in your comments. If you are asking (as you did in your comment above) what would happen if a virus with no enzymes were to infect a cell, see below.

In the case of HIV (and other retroviruses) some of the most important enzymes contained in a normal viral particle are:

  • A reverse transcriptase (RT): this enzyme reverse-transcribes the viral RNA genome to cDNA,
  • An integrase: incorporates the cDNA produced by the RT into the host cell's DNA.
  • A ribonuclease : an enzyme that can degrade (cut up) RNA. In the case of HIV this is the same protein as the RT.
  • A protease: an enzyme that can degrade other proteins.

Viruses work by copying their genetic material (their DNA or RNA) into the host cell's genome and then hijacking the cell's replication machinery to make more copies of the virus. So, what would happen if these enzymes were absent?

  • Without an integrase, the virus would not be able to insert its reverse transcribed DNA into the cell's genome.

  • Without an RT, the virus would not be able to copy its RNA into DNA.

  • The ribonuclease activity is also needed for successful reverse transcription to double stranded DNA (see [1] for a review and explanation of why.)

  • The protease is necessary for the formation of new viral particles. Mutations in this enzyme result in aberrantly assembled virus particles with low infectivity [2].

What you really must remember is that viruses are extremely streamlined. Everything they contain is essential. In some ways, you could say that viruses are the most highly evolved species (assuming they are living species), they are the most highly specialized "life forms" we know of and they have managed to get rid of all non-essential functions. The flip side of this is that everything that is left is essential, the virus cannot function without it.

So, to answer your question, a virus without any enzymes is, essentially, not a virus. It would not work, would not successfully infect cells.


  1. Greg L. Beilhartz and Matthias Götte, HIV-1 Ribonuclease H: Structure, Catalytic Mechanism and Inhibitors, Viruses 2010, 2:900-926

  2. Bukrinskaya A. HIV-1 matrix protein: a mysterious regulator of the viral life cycle. Virus Res. 2007 124(1-2):1-11.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .