Genome complexity: transposon functions (Introduction)

by David Turell , Monday, September 25, 2023, 20:19 (215 days ago) @ David Turell
edited by David Turell, Monday, September 25, 2023, 20:37

There are many:

https://phys.org/news/2023-09-transposons-selfish-genes-key-elements.html

"In 2001 the sequencing of the human genome revealed a surprising fact: over 45% of our genome comes from sequences called transposons, "jumping" genes that can move within the genome, generating new copies of themselves through molecular mechanisms of cut-and-paste or copy-and-paste.

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"Most of the copies generated by transposons are inactive today, but in the human genome and that of other mammals there are about a hundred copies of transposons belonging to the so-called LINE (Long Interspersed Nuclear Elements) family that are still potentially active. This means they can be transcribed, producing messenger RNAs that, when translated into proteins, can also contribute to a copy and paste process of genetic sequences.

"This ability of LINE transposons poses a potential risk to genome integrity: the random insertion of a new gene copy could interfere with important genetic functions. To protect against this danger, over the course of evolution, organisms have developed cellular defense mechanisms capable of blocking or limiting the activity of transposons, thus helping to preserve genome stability.

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"The key discovery is that LINE elements are recognized by protein complexes that initiate transcription processes essential for proper embryonic development.

"Federico Ansaloni, the study's lead author and former SISSA Ph.D. student, now a researcher at the Karolinska Institute in Stockholm, remarks, "Studying the very early stages of embryonic development allows us to outline the biological processes underlying the formation of a new individual. I find it fascinating that transposons, long considered junk DNA, are actually key elements in such a delicate process."

"Finally, the article "Exploratory analysis of L1 retrotransposons expression in autism," published in Molecular Autism, examines how LINE transposons behave in the brains of people with autism spectrum disorders. What the researchers discovered is that the transcription regulation of these sequences is different only in a small group of individuals with autism.

"The data analysis also identified a group of genes containing LINE copies that, when activated, suppress the transcription of the host genes, suggesting that these sequences contain specific signals recognized by cell regulatory mechanisms.

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"Remo Sanges, coordinator of the Ph.D. in Functional and Structural Genomics at SISSA and co-coordinator of the research, states, "It is fascinating to observe that, once the ability to identify transposon sequences evolved, our genome developed the ability to exploit these selfish elements to its advantage, using them as signals that can turn on or off entire transcriptional programs, making them indispensable for normal embryonic and brain development."

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"'With our research, it turns out that the most important functionality of these elements is at the RNA level and therefore independent of creating new copies. This discovery could explain why many copies of these elements are kept active and finely regulated in the genome of all living beings.'"

Comment: DNA is intrinsically packed with coded information and transposons are not jumping at random but in a controlled fashion. This cannot develop by chance. They are also related to aging:

https://phys.org/news/2023-09-transposable-elements-reveals-potential-methods.html

"The scientists have identified a specific process, called the Piwi-piRNA pathway, that helps control these TEs. They've seen this pathway at work in certain cells that don't age, like cancer stem cells, and notably, the enigmatic Turritopsis dohrnii, commonly known as the "immortal jellyfish." By strengthening this pathway in a worm called Caenorhabditis elegans, the worm lived significantly longer.[30%]

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"Additionally, the team found epigenetic changes in the DNA of these worms as they aged, specifically in the TEs. These changes, known as DNA N6-adenine methylation, was observed to increase TE transcription an jumping as the animal aged.

"Dr. Vellai emphasized the potential implications of this discovery: "This epigenetic modification may pave the way for a method to determine age from DNA, providing an accurate biological clock.'"

Comment: More functions will be found.