Posts Tagged ‘single stranded RNA’

Breakthrough in understanding folding of single stranded viral RNAs could lead to cure for the common cold

February 9, 2015 Leave a comment

Pretty cool stuff, not only is it the primary sequence, but all the secondary structural interacts are absolutely key for folding and assembly into the viral partciel.

Title overstates the case but excerpt from: Scientists have figured out how to stop the common cold in its tracks

“We have understood for decades that the RNA carries the genetic messages that create viral proteins, but we didn’t know that, hidden within the stream of letters we use to denote the genetic information, is a second code governing virus assembly,” one of the team, biophysicist Roman Tuma from the University of Leeds in the UK, told Laura Donnelly at The Telegraph. “It is like finding a secret message within an ordinary news report and then being able to crack the whole coding system behind it.”

Single-stranded RNA viruses are the most simple type of viruses known to science, and it’s thought that they were probably one of the first to evolve. And being around for a long time means they’re super-effective at what they do. Rhinovirus, which is the predominant cause of the common cold, is responsible for 1 billion infections per year – in the US alone.

Revealing the density of encoded functions in a viral RNA

We present direct experimental evidence that assembly of a single-stranded RNA virus occurs via a packaging signal-mediated mechanism. We show that the sequences of coat protein recognition motifs within multiple, dispersed, putative RNA packaging signals, as well as their relative spacing within a genomic fragment, act collectively to influence the fidelity and yield of capsid self-assembly in vitro. These experiments confirm that the selective advantages for viral yield and encapsidation specificity, predicted from previous modeling of packaging signal-mediated assembly, are found in Nature. Regions of the genome that act as packaging signals also function in translational and transcriptional enhancement, as well as directly coding for the coat protein, highlighting the density of encoded functions within the viral RNA. Assembly and gene expression are therefore direct molecular competitors for different functional folds of the same RNA sequence. The strongest packaging signal in the test fragment, encodes a region of the coat protein that undergoes a conformational change upon contact with packaging signals. A similar phenomenon occurs in other RNA viruses for which packaging signals are known. These contacts hint at an even deeper density of encoded functions in viral RNA, which if confirmed, would have profound consequences for the evolution of this class of pathogens.