Health & Medicine
Human Genome Evolved Through Internal Arms Race with Itself
Catherine Griffin
First Posted: Sep 29, 2014 10:04 AM EDT
When you hear about arms races, you don't normally think of genetics. Yet scientists have now found that you may just want to consider it when it comes to the genomes of primates. It's likely that an evolutionary arms race within these genomes drove the evolution of complex regulatory networks that orchestrate the activity of genes in every cell of our bodies.
The arms race in question is between mobile DNA sequences known as "retrotransposons," also known as jumping genes, and the genes that have evolved to control them.
"We have basically the same 20,000 protein-coding genes as a frog, yet our genome is much more complicated, with more layers of gene regulation," said Sofie Salama, one of the researchers, in a news release. "This study helps explain how that came about."
Retrotransposons are thought to be the remains of ancient viruses that infected early animals and inserted their genes into the genome long before humans evolved. Now they can only replicate themselves within the genome. Depending on where a new copy is inserted into the genome, a jumping event can disrupt the normal genes and cause disease, or remains neutral and simply adds to the overall size of the genome. Rarely, this causes an advantageous effect.
"There have been successive waves of retrotransposon activity in primate evolution, when a transposable element changed to become expressed and replicated itself throughout the genome until something turned it off," said Salama. "We've discovered a major mechanism by which the genome is able to shut down these mobile DNA elements."
The researchers identified repressors in the new study. These repressors belong to a large family of proteins known as "KRAB zinc finger proteins." These are DNA-binding proteins that repress gene activity, and constitute the largest family of gene-regulating proteins in mammals.
More specifically, the findings support the idea that expansion of this family of repressor genes occur in response to waves of retrotransposon activity, essentially creating an arms race. Because repression of a jumping gene can also affect genes located near it on the chromosome, it's possible that these repressors have been co-opted for other gene-regulatory functions.
"The way this type of repressor works, part of it binds to a specific DNA sequence and part of it binds other proteins to recruit a whole complex of proteins that creates a repressive landscape in the genome," said Salama. "This affects other nearby genes, so now you have a potential new layer of regulation available for further evolution."
The findings reveal a little bit more about humans may have evolved and a bit more about molecular evolution in general.
The findings are published in the journal Nature.
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First Posted: Sep 29, 2014 10:04 AM EDT
When you hear about arms races, you don't normally think of genetics. Yet scientists have now found that you may just want to consider it when it comes to the genomes of primates. It's likely that an evolutionary arms race within these genomes drove the evolution of complex regulatory networks that orchestrate the activity of genes in every cell of our bodies.
The arms race in question is between mobile DNA sequences known as "retrotransposons," also known as jumping genes, and the genes that have evolved to control them.
"We have basically the same 20,000 protein-coding genes as a frog, yet our genome is much more complicated, with more layers of gene regulation," said Sofie Salama, one of the researchers, in a news release. "This study helps explain how that came about."
Retrotransposons are thought to be the remains of ancient viruses that infected early animals and inserted their genes into the genome long before humans evolved. Now they can only replicate themselves within the genome. Depending on where a new copy is inserted into the genome, a jumping event can disrupt the normal genes and cause disease, or remains neutral and simply adds to the overall size of the genome. Rarely, this causes an advantageous effect.
"There have been successive waves of retrotransposon activity in primate evolution, when a transposable element changed to become expressed and replicated itself throughout the genome until something turned it off," said Salama. "We've discovered a major mechanism by which the genome is able to shut down these mobile DNA elements."
The researchers identified repressors in the new study. These repressors belong to a large family of proteins known as "KRAB zinc finger proteins." These are DNA-binding proteins that repress gene activity, and constitute the largest family of gene-regulating proteins in mammals.
More specifically, the findings support the idea that expansion of this family of repressor genes occur in response to waves of retrotransposon activity, essentially creating an arms race. Because repression of a jumping gene can also affect genes located near it on the chromosome, it's possible that these repressors have been co-opted for other gene-regulatory functions.
"The way this type of repressor works, part of it binds to a specific DNA sequence and part of it binds other proteins to recruit a whole complex of proteins that creates a repressive landscape in the genome," said Salama. "This affects other nearby genes, so now you have a potential new layer of regulation available for further evolution."
The findings reveal a little bit more about humans may have evolved and a bit more about molecular evolution in general.
The findings are published in the journal Nature.
See Now: NASA's Juno Spacecraft's Rendezvous With Jupiter's Mammoth Cyclone