Monday, August 25, 2008


I was just checking that something I said today was correct when I found out that something else I said was incorrect....

First, the correct bit. Yes, in answer to the question, HIV and other retroviruses contain genes that code for the reverse transcriptase they need to replicate.

However I think I then said that reverse transcriptase would not normally be found in human cells. (After all it's called reverse transcriptase for a reason - transcription usually goes from DNA to RNA).

But I was totally forgetting about transposons, in particular, a type of transposon called a retrotransposon. You might have heard of transposons referred to as 'jumping genes' for their ability to move about within the genome. Retrotransposons achieve this trick by being transcribed to RNA and then back to DNA in their new position. This transcription from RNA back to DNA occurs via, you guessed it, a type of reverse transcriptase. Since their discovery in the 1980's it has been found that retrotranspons are common in the genomes of animals and, in particular, plants.

Targeting reverse transcriptase is still a viable strategy for HIV drugs though and HIV drugs such as Retrovir, Epivir, Viread and Viramune are all reverse transcriptase inhibitors.

In a link to earlier lectures, transposons in bacteria can carry genes for antibiotic resistance and are capable of moving these genes from chromosomal DNA to plasmid DNA and back again. This is an important mechanism in the acquisition of multi-drug resistance.

This might be a bit much biology for some of you but I thought it was interesting.

Relevant material previously on the blog:
Endogenous retroviruses (read the New Yorker article on endogenous retroviruses, it's excellent)
The Lost Children of Rockdale County (links to the PBS program I referred to in class)
STD versus STI

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