Handbook here.
Transcription indeed involves a step resembling the motion of a vehicle: Enzymes “ride” along gene “tracks,” creating molecules that will later be translated into the various proteins involved in the life of the cell. In the new study, a research team headed by Prof. Rivka Dikstein of the Biological Chemistry Department has found that just as on the road, maintaining a reasonable distance between the vehicles — that is, the transcribing enzymes — is the surest way to reach a destination safely.
Weizmann Institute researchers tried jiggering the system, and
When the transcription enzymes were launched in bursts, the amount of the resultant microRNA dropped; conversely, when the enzymes were launched at greater intervals, production of microRNA was more efficient.
It turned out that when the enzymes were launched in bursts, one rapidly following the next, they ended up in a traffic jam: When the first enzyme paused at a “speed bump” — a molecular signal that creates a pause in transcription — the enzymes that followed crashed into it, falling off the gene. Naturally, such “traffic accidents” reduced the amount of resultant microRNA. In contrast, when the enzymes were launched one by one, they maintained a safe distance: Each had sufficient time to slow down at the “bump” and to succeed at creating a microRNA molecule. In other words, the lower rate of release of individual enzymes proved to be a more efficient method for creating microRNAs.
File under: It’s this way because otherwise it wouldn’t have worked so well, that’s all.
Also:
Finally, this study helps explain an earlier finding in Dikstein’s lab: In longer genes, transcription enzymes tend to be launched at a low rate, that is, at great intervals. The longer the gene, the greater the risk that it has molecular “bumps” that can create traffic jams, derailing transcription. Therefore, transcription enzymes riding along such genes at a lower rate can do their job more efficiently than the enzymes launched in rapid bursts.