Breaking the Dogma - How Retroviruses Rewrite Our DNA
Cellsius, a community biotech lab in SF, hosted its monthly wetware meetup last Friday. I genuinely enjoyed all the conversations I had there. The atmosphere was buzzing with curiosity, and the topics we covered ranged from organoid intelligence and microscopy, to AI-driven drug discovery and RNA molecule shape prediction.
Among all these exciting conversations, the biggest surprise came from a conversation about retroviruses. I didn’t know that there is an exception to the central dogma of molecular biology: the flow of genetic information from DNA to RNA to proteins. Retroviruses flip the central dogma on its head.
A biotech startup founder explained this to me while walking me through his startup idea. He shared how retroviruses like HIV don’t follow the usual DNA-to-RNA route. Most viruses use DNA to make copies of themselves, but retroviruses use RNA instead.
Retroviruses enter a host cell and turn their own RNA into DNA using an enzyme called reverse transcriptase as they reverse the transcription process (usually DNA to RNA). That reverse-transcribed DNA then travels into the nucleus, where another enzyme called integrase helps insert it into the host’s own DNA. It becomes part of the host’s genetic material, which means its cells start making more of the virus as the cells replicate themselves. Since the virus is now part of your DNA, it’s very hard to get rid of. That’s why some retroviruses can cause long-term infections.
At home, I learned that retroviruses are just one example of reverse transcription. Other instances include retrotransposons, genetic elements that can copy and insert themselves into different parts of the genome, and Hepatitis B virus, which also uses reverse transcription as part of its life cycle.
Interestingly, I also learned that reverse transcription is just one of several exceptions to the central dogma of molecular biology. Other exceptions include prions, which are infectious proteins that replicate without nucleic acids, and RNA viruses, which replicate their RNA genomes without involving DNA at all.
Seen in this broader context, reverse transcription isn’t so surprising. In fact, the RNA World Hypothesis—which posits that RNA came before DNA in the early stages of life on Earth—suggests that the ability to convert RNA into DNA may have been a key evolutionary development. Over time, enzymes like reverse transcriptase may have enabled the shift from an RNA-based world to the DNA-based genetic systems we see today.