Biology Textbooks Wrong? New Research Reveals the Secret Behind a Key Cellular Process - SciTechDaily

During transcription, an enzyme called RNA polymerase wraps itself around the double helix of DNA, using one strand to match nucleotides to make a copy of genetic material — resulting in a newly synthesized strand of RNA that breaks off when transcription is complete.

“We started studying Rho, and realized it cannot possibly work in ways people tell us it works,” said Irina Artsimovitch, co-lead author of the study and professor of microbiology at The Ohio State University.

The research, published online by the journal Science today, November 26, 2020, determined that instead of attaching to a specific piece of RNA near the end of transcription and helping it unwind from DNA, Rho actually “hitchhikes” on RNA polymerase for the duration of transcription.

The team used sophisticated microscopes to reveal how Rho acts on a complete transcription complex composed of RNA polymerase and two accessory proteins that travel with it throughout transcription.

“This is the first structure of a termination complex in any system, and was supposed to be impossible to obtain because it falls apart too quickly,” Artsimovitch said.

“It answers a fundamental question — transcription is fundamental to life, but if it were not controlled, nothing would work.

While traveling with RNA polymerase, Rho can tell if the synthesized RNA is worth making — and if not, Rho releases it.”.

Artsimovitch has made many important discoveries about how RNA polymerase so successfully completes transcription.

Because of that, Artsimovitch said, it has never made sense that Rho looks only for specific RNA sequences, without even knowing if they are still attached to RNA polymerase.

In fact, the scientific understanding of the Rho mechanism was established using simplified biochemical experiments that frequently left out RNA polymerase — in essence, defining how a process ends without factoring in the process itself.

This high-resolution visualization, combined with high-end computation, made accurate modeling of transcription termination possible.

The complex is extremely stable because it has to be — if the RNA is released, it is lost,” Artsimovitch said.

Using a clever method to trap complexes just before they fall apart enabled the scientists to visualize seven complexes that represent sequential steps in the termination pathway, starting from Rho’s engagement with RNA polymerase and ending with a completely inactive RNA polymerase.

Though the study was conducted in bacteria, Artsimovitch said this termination process is likely to occur in other forms of life.

November 24, 2020

November 24, 2020