What? It turns out it is not junk. It needs managing but it isn’t junk.
The human genome is fascinating. Once predicted to contain about a hundred thousand protein-coding genes, it now seems that the number is closer to twenty thousand, and maybe less. And although our genome is made up of about three billion units — “base pairs” — many of them don’t seem to belong to specific genes, and for that reason they were delegated to the dustbin of genetics: they were literally called “junk DNA.”
But as it turned out, junk DNA is actually critical in coordinating and regulating the work of actual genes. For example, there are sequences of DNA that “jump” around the genome and influence gene expression. These jumping units are called “transposable elements” and their number is estimated at over 4.5 million in a single genome.
In short, the genome is nothing like what we were led to believe.
But now get this:
When the genome of the human embryo is activated shortly after the egg is fertilized by the sperm, transposable elements are among the first sequences to be expressed. The researchers found that KZFPs quickly “tame” these elements, minimizing their transcriptional impact during the earliest stages of early embryogenesis. This allows transposable elements to be subsequently used later in development and in adult tissues. In this way, KZFPs play a key role in defining how the human genome is regulated, by facilitating the incorporation of transposable element-based controlling sequences into transcriptional networks.
“Our results reveal how a family of proteins that was long considered an oddity of nature, turns foes into friends,” says Didier Trono. “They show that KZFPs do not just sentence transposable elements to perpetual silence, but domesticate their formidable regulatory potential for the benefit of our genome. But our findings also imply that anomalies in the completion of this process would fatally compromise the earliest phases of human embryonic development.” Paper. (open access) – Julien Pontis, Evarist Planet, Sandra Offner, Priscilla Turelli, Julien Duc, Alexandre Coudray, Thorold W. Theunissen, Rudolf Jaenisch, Didier Trono. Hominoid-Specific Transposable Elements and KZFPs Facilitate Human Embryonic Genome Activation and Control Transcription in Naive Human ESCs. Cell Stem Cell, 2019; DOI: 10.1016/j.stem.2019.03.012 More.
“Our results reveal how a family of proteins that was long considered an oddity of nature, turns foes into friends,” says Didier Trono? And almost nothing the Darwinians told us is true.
See also: Reproductive stem cells have a plan to fight off jumping genes
Jumping genes drive changes in strawberries
Researchers: Jumping genes time their activity, await opportunity
Researchers: Jumping genes play extensive role in human evolution
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