Hollywood editors in the old school cut out unwanted footage of film and stick to the desired footage to make a movie. The human body does something like this – trillions of times per second – through a biochemical editing process called RNA interlacing. Instead of cutting a movie, he edits the messenger RNA, which is the basis for the production of many proteins in the cells.
In his study of evolutionary origins and the history of RNA splicing and the human genome, UC San Diego Navtej Toor and Daniel Haack biochemists combine two-dimensional (2-D) images of individual molecules to reconstruct three-dimensional (3-D) picture of part of RNA – what scientists call introns of group II. In this way, they discovered a large molecular movement associated with RNA catalysis that provides evidence of the origins of RNA splicing and its role in the diversity of life on Earth. Their drills are outlined in the current issue of Cell .
"We are trying to understand how the human genome has evolved, starting with primitive ancestors: Every human gene has unwanted fragments that are not encoded and must be removed before gene expression is the process of RNA splicing "said Toor, an associate professor in the Department of Chemistry and Biochemistry, adding that 15 percent of human illnesses are the result of defects in this process.
Toor explained that his team is working to understand the evolutionary origin of 70 percent of human DNA – a part made up of two types of genetic elements believed to have evolved from group II introns. In particular, the splice-inosome introns, which make up about 25 percent of the human genome, are non-coding sequences to be deleted before gene expression. The remaining 45 percent consist of sequences derived from the so-called retro-elements. These are genetic elements that are inserted into the DNA and jump around the genome to replicate through the RNA intermediate.
"The study of group II introns gives us an idea of the evolution of much of the human genome," notes Toor.  Working with a nanomachine from intron II RNA, Toor and Haak, UC San Diego, PhD, and the first author of the article, managed to isolate intron complexes from the group of blue-green algae species that live high
of group II introns from a high temperature organism made it easier to determine the structure due to the inherent stability of the complex of this species, "says Haak. "The evolution of this type of RNA splicing has probably led to a diversification of life on Earth."
Haak also explains that he and Tor revealed that the intron of group II and the spleneidosome had a dynamic dynamic mechanism to move their catalytic components time of
"This is the strongest evidence to date that the spleneysome has evolved from an intron of bacterial group II," he said.
Furthermore, the findings reveal how Group II introns are capable of inserting into DNA by a process called retransposition. This copying and placement process has led to the propagation of egotistical retro-elements in human DNA to consist of much of the genome.
"The replication of these retro-elements plays a major role in shaping the architecture of the modern human genome and even has
Researchers use cryo-electron microscopy (cryo-EM) to derive a molecular structure from a Group II intron. a layer of thin ice and then fired electrons through this sample, according to scientists, the electron microscope could magnify the image 39,000 times.The resulting 2D images of individual molecules were then harvested to create a 3-D view of an intron from a group II.  "It's like molecular archeology," Haak described. "The introns of group II are living fossils that give us an idea of how complex life has developed for the first time on Earth."
Predict how splicing errors affect the risk of illness
Daniel B. Haack et al., Cryo-EM Structures of Intron Reverse Splicing into DNA, Cell (2019). DOI: 10.1016 / j.cell.2019.06.035
Like film editors and archaeologists, biochemists unite history of the genome (2019, July 27)
drawn up on 27 July 2019
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