The Simplest Answer
The simplest answer isn’t always right, but it’s often one of the most convincing answers. John Timmer over at Ars Technica talks about the rise of a very simple answer to a whole swath of questions that include
- How do transcription factors, splicing factors, and other such DNA and RNA interacting proteins operate accurately when they’re so promiscuous in what they choose to bind to?
- Why is so much of the DNA transcribed to RNA?
The simple answer that John gives is simply, transcription and splicing factors don’t operate that accurately, and most of the DNA is transcribed to RNA because of this inaccuracy. Simple! And quite a compelling theory, actually, something I like very much.
The question this line of reasoning raises, then, is whether the RNA editing and selective degradation pathways are sufficient to prevent something bad from happening to the cell. There’s nonsense-mediated decay, signal-sequence localization, non-stop mediated decay, and complicated RNA localization and export control. That’s in addition to RNAi, the evolution of which may have been driven in large part in order to weed out bad RNA.
This would, perhaps, explain why RNA editing features are so much more complicated in mammalian cells than in Saccharomyces cerevisiae, as S. cerevisiae (baker’s yeast) tends to have very highly conserved, high-consensus splice sequences (i.e. low error, but also low complexity), as well as more well-defined and static chromatin and no RNAi.
The story vindicates that complicated gene regulation and patches and makeshift fixes for errors are two sides of the same coin.
