Traffic in Los Angeles is horrendous.
But it would be even worse during rush hour if the freeway on-ramps weren’t metered. Stoplights regulate the number of cars permitted to merge onto the freeway. This pause causes a backup in the merging lane, but improves overall traffic flow. So, it is worth it for motorists to wait a few minutes to merge in exchange for a shorter time in traffic.
Recently, a team of biochemists from the Weizmann Institute in Israel discovered that the same principles used by traffic engineers are at work inside the cell during transcription.1 Transcription refers to the processes employed by the cell’s biochemical apparatus to decode the information stored in DNA, and ultimately, to produce proteins—large complex molecules that carry out all the activities in the cell.
Transcription begins when a protein called an RNA polymerase binds to a region of DNA called a promoter. The promoter sequence is part of the transcription initiation site. Once RNA polymerase latches on, this enzyme moves along the DNA—like a car traveling on a highway—and produces an RNA molecule. Depending on the specific region of the DNA read by the RNA polymerase, the newly minted transcript can be used to make a protein at the ribosomes or to regulate the production of other RNA molecules.
While studying the production of a particular class of regulatory RNAs (called microRNAs), the Weizmann Institute investigators discovered that transcript production decreased when the transcription initiation rate increased. On the other hand, decreasing the initiation rate led to increased microRNA manufacture.
Researchers explained this counterintuitive observation when they uncovered evidence for pause sites during the transcription of microRNAs. At these sites, the RNA polymerase enzyme slows down. Each time initiation takes place, a new RNA polymerase enzyme latches onto the DNA and begins its journey along the double helix. If initiation rates are high, then a traffic jam ensues. As a result of the traffic backup, RNA polymerase molecules will collide with one another at the pause sites. This biochemical traffic jam leads to a premature termination of transcription as the RNA polymerases are jolted off the DNA from the impact of the collision. But if initiation rates are low, then the RNA polymerase enzymes have time to move past the pause sites before a backup occurs, successfully completing transcription.
This study shines light onto the elegant and clever processes that typify biochemical systems. Along these lines, it is intriguing to note how the molecular logic of biochemical systems—metering initiation leads to improved traffic flow along the DNA molecule––displays remarkable similarity to the type of logic employed by civil engineers when they design systems to regulate the flow of traffic.
As I discuss in The Cell’s Design, the analogy between human and biochemical designs, like this discovery on the regulation of transcription, refuels the Watchmaker argument for God’s existence and strengthens the scientific case for a Creator.