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• Time of issue:2018-09-28
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(Summary description)
Many processes that take place in cells are integral to life. As two of them, transcription and translation allow the genetic information stored in DNA to be decoded into the proteins that form the proteins of all organisms such as bacteria, plants and humans.

Scientists have known for half a century that the two processes are coupled in bacteria, but until now, they didn't know how. Now, in a new study, researchers from the University of Wisconsin-Madison (UW-Madison) and the Max Planck Institute for Biophysical Chemistry in Germany have revealed that a so-called "expressome" the exact structure of the complex. The results of the study were published in the April 14, 2017 issue of Science, with the title "Architecture of a transcribing-translating expressome". The corresponding authors of the paper are Robert Landick, a professor in the UW-Madison Department of Biochemistry, and Patrick Cramer, director of the Max Planck Institute for Biophysical Chemistry.

The researchers say the study using the model organism Escherichia coli could help to understand how the bacteria affect human health, including better understanding gene regulation and developing new antibiotics.

Landick explained, "The existence of this complex in bacteria has been proposed based on evidence, but so far, no one has confirmed its existence. This study is the first to demonstrate the ability to harness these two already complex machines. (i.e. transcription complex, or transcription machinery; translation complex, or translation machinery) forms a larger supercellular machinery (i.e. expressosome)."

The transcription process uses RNA polymerase to convert DNA into RNA. Following this process, another molecular machine called the ribosome translates this RNA (more specifically, signaling RNA, or mRNA) into a protein that the bacteria can use to function.

Rachel Mooney, a researcher in UW-Madison's Department of Biochemistry, said that in bacterial expressosomes, RNA polymerase and ribosomes form a complex structure to carry out the two processes in a coupled fashion, and the newly resolved The expression body structure helps to understand how this happens.

Transcription and translation also occur in animals and humans, but the two processes are not coupled as in bacteria. Instead, they occur in two physically distinct parts of the cell. If scientists can discover a way to disrupt this expressosome, they may be able to develop drugs that target bacteria but do not harm human cells, the researchers said.

These findings also extend to the study of the microbiome (the population of microbes in and on the human body). Ongoing research demonstrates how important the microbiome is to human health, and understanding gene regulation in these microbial populations is a vital part of these efforts. Today, this expressosome structure is the basis for this understanding.

"In human biology, we tend to think of what happens in human cells, but there are at least as many bacterial cells inside and on our bodies as there are human cells," Landick said. is not common, then we used it as a model organism to extend our research to other bacteria that are critical to human processes."

Landick, Mooney (UW-Madison team) collaborated with Cramer and Rebecca Kohler (German team) on the study. Equipment provided by the German team assisted in deciphering the structure of the expressosome. This expression body contains RNA polymerase provided by the UW-Madison team.

"Our study explains past observations that these two processes (transcription and translation) are coupled together in these bacterial cells," Cramer said.

Researchers are also interested in the origin of this complex. Why these two processes are coupled in bacteria but not in organisms such as humans needs to be studied from an evolutionary perspective.

Landick explained, "One of the arguments against it is to simply think that bacteria are far ahead of us in evolution. It's counterintuitive, but only technically, they have far more descendants than us. Bacteria The evolutionary pressures faced have led to this very integrated and very efficient approach to transcribing and translating DNA into protein."