Viewing a single comment thread. View all comments

Mamanfu t1_j4xajh3 wrote

First off I would like to say that all you scientists are amazing. Your knowledge in the field is inspirational bc those up and coming want to be like you and just understand this block we call earth! I was looking at the mechanism of action for a retrovirus. Specifically HIV. When it enters the cell, it immediately unpacks and enzymes begin to reverse transcribe RNA to DNA. After this time it enters the nucleus of the host cell. What? That's a red flag. As far as I know, never would the cell need DNA of ANY KIND to flow INTO the nucleus. According to the central dogma, the only thing flowing OUT of the nucleus is mRNA. Wouldn't this provide a weakness. If we were to be able to prevent viral DNA which is structurally and fundamentally different from RNA from getting past the nuclear envelope, we could nip this in the bud.

1

marieterna t1_j4xd6f4 wrote

First, DNA/RNA can actually enter the nucleus. Nuclear import is controlled by special amino acid sequences known as nuclear localization sequences. This, along with importin (transport protein) allows macromolecules to enter the nucleus through the nuclear pore complexes. tRNA, for example, are imported back into the nucleus, which has been shown in yeast. Plasmid DNA import has also been demonstrated.

When a cell divides, it’s nuclear envelope breaks down, so the mitotic spindle apparatus can invade and attach to the chromosomes. Then, the viral nucleic acids can interact with the hosts’. HIV, howeve, can enter the nucleus even if the cell isn’t dividing. It’s thought that the HIV genome uses the host’s cellular machinery to move into the nucleus. The HIV cDNA (result of reverse transcription) is coated with a myriad of proteins which allow it to cross into the nucleus.

Figure 1 in this paper should give you a good visualization: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3325773/

TL;DR: HIV sneaky. :( The idea of the central dogma of biology has some loopholes, with reverse transcription, and direct translation from DNA to protein. Always* exceptions to rules, that’s what makes science so amazing.

3

123frogman246 t1_j4xetta wrote

Viruses = sneaky. Hijacking a cell's own mechanisms to replicate and go on to infect more cells.

1

marieterna t1_j4xfelh wrote

About the central dogma of molecular biology, it doesn’t necessarily specify locations. Prokaryotes lack a nucleus and instead have a nucleoid, yet still follow the general basis of the central dogma. The central dogma moreso specifies products, DNA to RNA to protein.

1