CHICAGO, April 15 (Xinhua) -- University of Michigan (UM) researchers have directly observed previously hidden RNA regulatory mechanisms within so-called "transcription-translation coupling," wherein the first ribosome can immediately follow and couple with the transcribing RNA polymerase.
The researchers expanded a combination of single-molecule fluorescence microscopy techniques to monitor the dynamic interactions of the transcription and translation machineries during different stages of coupling. They also developed a unique strategy to directly watch transcription-translation coupling in real-time.
They detected that the small riboswitch controls the much larger transcription and translation machineries.
The researchers found that modulating the translation of a nascent mRNA affects the downstream synthesis of the mRNA itself. When translation is stopped or delayed, the transcription rate is slowed down to avoid overproduction of RNA that would only be degraded in the cell.
To conveniently modulate translation efficiency, the researchers exploited the features of a structured RNA, called a translational riboswitch, embedded near the start of an mRNA of the anthrax bacterium Bacillus anthracis. This RNA changes structure when binding a specific small ligand to reduce translation in response to environmental cues.
"With RNA emerging as a major factor in our daily lives -- note the SARS-CoV-2 viral genome and the mRNA vaccines to combat its replication -- we are at a crossroads where the interplay between RNAs and proteins in their ubiquitous complexes becomes an attractive prospective target for the medicines of the future, including to fight drug-resistant bacterial strains," said senior author Nils Walter, a professor of chemistry.
The current study shows that the riboswitch, generally thought to only affect translation, can in fact regulate both translation and transcription by exploiting their coupling. By using the riboswitch ligand to slow translation initiation, or inhibitors to delay or stop translation, the researchers observed effects also on the speed of RNA polymerase.
The results, posted on UM's website on Wednesday, have been published in the Proceedings of the National Academy of Sciences. Enditem