Richard P Grant and his BioLOG (biolog); the wee blog, weblog, or web blog; things not necessarily biology related. The anti-blogger.


3 June 2010

On coupling

No, not that sort of coupling.

I was writing up today’s Faculty Dailies, catching up on (yet) another paper about how ribosomes control the rate of transcription.

As has been known for decades, bacterial transcription and translation are tightly coupled. What’s interesting about the recent work is that the presence/processivity of the ribosome appears to feedback on the rate of transcription by stopping the RNA polymerase from going backwards. (I can’t help but think there’s also a link between this phenomenon and the observation that rare codons slow translation, but that’s something else to worry about.)

Now, when I was working on nuclear trafficking I managed to get our lab’s website into the first page of Google hits for that term (about third, I think). That’s irrelevant: what is relevant is that I left the field nearly five years ago, and at that time we all assumed that, just as in bacteria, translation and transcription were tightly coupled in eukaryotes. How can this be, seeing as they’re in separate compartments? Well, we figured that the messenger RNA was being exported through nuclear pores while the arse-end was still being transcribed. All the RNA-binding proteins seemed to interact with enough of each other that we could happily hypothesize a continuum from chromatin through RNA polymerase through the splicing machinery to the nuclear pore.

Besides, we couldn’t figure out what made mRNA go in one direction through the pore (i.e., out)—although we were pretty certain that it was ribosomes clamping down on the mRNA as it poked out of the nuclear pore, stopping it going back in, and equilibrium dynamics doing the rest (in much the same way this paper postulates that preventing back-tracking is how ribosomes control RNA polymerase)—so this made intuitive sense and seemed to answer a lot of awkward questions. The actual mechanics were simply a matter of time, we figured.

So, coming back to this morning, I was a little surprised to find the sentence

In contrast to bacteria, transcription and translation in eukaryotes take place in different cellular compartments and are not coupled

in a Research Highlight in Nature Reviews Genetics.

Um, has the field done a complete volte-face while I was noodling away at zinc fingers and websites? Were we wildly ahead of our time, or just completely wrong? What is the latest thinking on this? Anybody got a Stryer?

Filed under: Uncategorized — rpg @ 20:05


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