Why are some bacterial genes high in purines?
In the study of bacteria, a longstanding dogma held that two molecular machines — RNA polymerase, which leads the way in transcribing DNA into RNA, and ribosomes, which bring up the rear translating RNA into proteins...
This close coupling of transcription and translation in bacteria was thought to be fundamental to gene expression in part because the trailing ribosome could shield nascent gene products from an effective and omnipresent quality-control protein called Rho.
In bacteria that exhibit something called runaway transcription, however, the polymerase instead speeds ahead, unhitched from its protective ribosome. Inexplicably, however, in bacteria that exhibit this runaway transcription, such as Bacillus subtilis , Rho targeted primarily noncoding, useless RNA products.
New research from the Department of Biology reveals that the secret to Rho’s quality-control specificity lies in the sequence composition of nucleotide bases that make up coding strands of DNA.
“We started with a hypothesis that Rho was regulated by sequence, but the fact that the sequence alone was enough to protect any gene in the entire B. subtilis genome from Rho was really surprising,” says Julia Dierksheide PhD ’26, a graduate student in the Li Lab and first author of a paper recently published in Nature Microbiology . “That’s a really diverse range of sequences — what sequence feature is shared by every single gene in the genome?”
Rho serves as a termination factor, meaning that it is a crucial mechanism for preventing bacteria from wasting precious resources by making RNA transcripts that serve no purpose.