Discovery of Intron Function Interrupts Evolutionary Paradigm

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BY FAZALE RANA – MARCH 6, 2019

Nobody likes to be interrupted when they are talking. It feels disrespectful and can be frustrating. Interruptions derail the flow of a conversation.

The editors tell me that I need to interrupt this lead to provide a “tease” for what is to come. So, here goes: Interruptions happen in biochemical systems, too. Life scientists long thought that these interruptions disrupted the flow of biochemical information. But, it turns out these interruptions serve an important function, offering a rejoinder a common argument against intelligent design.

Now back to the lead.

Perhaps it is no surprise that some psychologists study interruptions1 with the hope of discovering answers to questions such as:

  • Why do people interrupt?
  • Who is most likely to interrupt?
  • Do we all perceive interruptions in the same way?

While there is still much to learn about the science of interruptions, psychologists have discovered that men interrupt more often than women. Ironically, men often view women who interrupt as ruder and less intelligent than men who interrupt during conversations.

Researchers have also found that a person’s cultural background influences the likelihood that he or she will interrupt during a discourse. Personality also plays a role. Some people are more sensitive to pauses in conversation and, therefore, find themselves interrupting more often than those who are less uncomfortable with periods of silence.

Psychologists have learned that not all interruptions are the same. Some people interrupt because they want the “floor.” These people are called intrusive interrupters. Cooperativeinterrupters help move the conversation along by agreeing with the speaker and finishing the speaker’s thoughts.

Interruptions are not confined to conversations. They are a part of life, including the biochemical operations that take place inside the cell.

In fact, biochemists have discovered that the information harbored in genes, which contains the instructions to build proteins—the workhorse molecules of the cell—experience interruptions in their coding sequences. These intrusive interruptions would disrupt the flow of information in the cell during the process of protein synthesis if the interrupting sequences weren’t removed by the cell’s machinery.

Molecular biologists have long viewed these genetic “interruptions” (called introns) as serving no useful purpose for the cell, with introns comprising a portion of the junk DNA found in the genomes of eukaryotic organisms. But it turns out that introns—like cooperative interruptions during a conversation—serve a useful purpose, according to the recent work of two independent teams of molecular biologists.

Introns Are Abundant

Noncoding regions within genes, introns consist of DNA sequences that interrupt the coding regions (called exons) of a gene. Introns are pervasive in genomes of eukaryotic organisms. For example, 90 percent of genes in mammals consists of introns, with an average of 8 per gene.

After the information stored in a gene is copied into messenger RNA, the intron sequences are excised, and the exons spliced together by a protein-RNA complex known as a spliceosome.

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Figure 1: Drawing of pre-mRNA to mRNA. Image credit: Wikipedia

Molecular biologists have long wondered why eukaryotic genes would be riddled with introns. Introns seemingly make the structure and expression of eukaryotic genes unnecessarily complicated. What possible purpose could introns serve? Researchers also thought that once the introns were spliced out of the messenger RNA sequences, they were discarded as genetic debris.

Introns Serve a Functional Purpose

But recent work by two independent research teams from Sherbrooke University in Quebec, Canada, and MIT, respectively, indicates that molecular biologists have been wrong about introns. They have learned that once spliced from messenger RNA, these fragments play a role in helping cells respond to stress.

Both research teams studied baker’s yeast. One advantage of using yeast as a model organism relates to the relatively small number of introns (295) in its genome.

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Figure 2: A depiction of baker’s yeast. Image credit: Shutterstock

Taking advantage of the limited number of introns in baker’s yeast, the team from Sherbrooke University created hundreds of yeast strains—each one missing just one of its introns. When grown under normal conditions with a ready supply of available nutrients, the strains missing a single intron grew normally—suggesting that introns aren’t of much importance. But when the researchers grew the yeast cells under conditions of food scarcity, the yeast with the deleted introns frequently died.2

The MIT team observed something similar. They noticed that during the stationary phase of growth (when nutrients become depleted, slowing down growth), introns spliced from RNA accumulated in the growth medium. The researchers deleted the specific introns that they found in the growth medium from the baker’s yeast genome and discovered that the resulting yeast strains struggled to survive under nutrient-poor conditions.3

At this point, it isn’t clear how introns help cells respond to stress caused by a lack of nutrients, but they have some clues. The Sherbrooke University team thinks that the spliced-out introns play a role in repressing the production of proteins that help form ribosomes. These biochemical machines manufacture proteins. Because protein synthesis requires building block materials and energy, during periods when nutrients are scarce, protein production slows down in cells. Ratcheting down protein synthesis impedes cell growth but affords them a better chance to survive a lack of nutrients. One way cells can achieve this objective is to stop making ribosomes.

The MIT team thinks that some spliced-out introns interact with spliceosomes, preventing them from splicing out other introns. When this disruption happens, it slows down protein synthesis.

Both research groups believe that in times when nutrients are abundant, the spliced-out introns are broken down by the cell’s machinery. But when nutrients are scarce, that condition triggers intron accumulation.

At this juncture, it isn’t clear if the two research teams have uncovered distinct mechanisms that work collaboratively to slow down protein production, or if they are observing facets of the same mechanism. Regardless, it is evident that introns display functional utility. It’s a surprising insight that has important ramifications for our understanding of the structure and function of genomes. This insight has potential biomedical utility and theological implications, as well.

Intron Function and the Case for Creation

Scientists who view biology through the lens of the evolutionary paradigm are quick to conclude that the genomes of organisms reflect the outworking of evolutionary history. Their perspective causes them to see the features of genomes, such as introns, as little more than the remnants of an unguided evolutionary process. Within this framework, there is no reason to think that any particular DNA sequence element, including introns, harbors function. In fact, many life scientists regard the “evolutionary vestiges” in the genome as junk DNA. This clearly has been the case for introns.

Yet, a growing body of data indicates that virtually every category of so-called junk DNA displays function. We can now add introns—cooperative interrupters—to the list. And based on the data on hand, we can make a strong case that most of the sequence elements in genomes possess functional utility.

Could it be that scientists really don’t understand the biology of genomes? Or maybe we have the wrong paradigm?

It seems to me that science is in the midst of a revolution in our understanding of genome structure and function. Instead of being a wasteland of evolutionary debris, most of the genome appears to be functional. And the architecture and operations of genomes appear to be far more elegant and sophisticated than anyone ever imagined—at least within the confines of the evolutionary paradigm.

But what if the genome is viewed from a creation model framework?

The elegance and sophistication of genomes are features that are increasingly coming into scientific view. And this is precisely what I would expect if genomes were the product of a Mind—the handiwork of a Creator.

Now that is a discovery worth talking about.

Resources

Endnotes
  1. Teal Burrell, “The Science behind Interrupting: Gender, Nationality and Power, and the Roles They Play,” Post Magazine (March 14, 2018), https://www.scmp.com/magazines/post-magazine/long-reads/article/2137023/science-behind-interrupting-gender-nationality; Alex Shashkevich, “Why Do People Interrupt? It Depends on Whom You’re Talking To,” The Guardian (May 18, 2018), https://www.theguardian.com/lifeandstyle/2018/may/18/why-do-people-interrupt-it-depends-on-whom-youre-talking-to.
  2. Julie Parenteau et al., “Introns Are Mediators of Cell Response to Starvation,” Nature 565 (January 16, 2019): 612–17, doi:10.1038/s41586-018-0859-7.
  3. Jeffrey T. Morgan, Gerald R. Fink, and David P. Bartel, “Excised Linear Introns Regulate Growth in Yeast,” Nature 565 (January 16, 2019): 606–11, doi:10.1038/s41586-018-0828-1.

Reprinted with permission by the author
Original article at:
https://www.reasons.org/explore/blogs/the-cells-design/read/the-cells-design/2019/03/06/discovery-of-intron-function-interrupts-evolutionary-paradigm

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