First 'movie' of influenza virus genome multiplication obtained

Researchers at IMDEA Nanoscience have observed live, for the first time, the multiplication of the genome of the influenza A virus. This fact will help to understand some of the factors that determine the speed of multiplication of this infectious microorganism.

El influenza A virus is a major threat to public health. Understanding how this virus replicates is crucial, especially since its mutations can give rise to new strains capable of affecting humans. At the core of the virus is genetic information, contained in RNA chains –ribonucleic acid-, which the polymerase enzyme is responsible for copying to generate new viruses.

RNA chains are covered by proteins that protect the RNA from being degraded inside cells. How does the polymerase get multiply RNA efficiently if it is completely covered in proteins? And furthermore, how does it manage to copy the RNA without uncoupling it from the proteins that protect it?

During the process of RNA replication, the viral polymerase moves through the RNA structure, synthesizing and copying the structure. The proteins that protect the RNA of the influenza A virus genome are organized in a compact double helix, masking the position of the polymerase.

During the process of RNA multiplication, the viral polymerase moves through the RNA structure, synthesizing and copying the structure.

Because the polymerase cannot be observed directly in action, many details of the 'copying' process remain hidden from view. To date, it has not been possible to follow the movement and activity of the polymerase along the viral genome.

The 'Manipulation of Molecular Motors' research group of the Madrid Institute for Advanced Studies in Nanoscience, led by Borja Ibarra, in collaboration with researchers from NanoLSI (Kanazawa University, Japan) and the National Center for Biotechnology (CNB-CSIC), have devised a strategy that is key to studying this elusive process in detail.

Researchers shortened the virus's genome to make the proteins that protect it form a ring, rather than a helix. In this way, the position of the polymerase is revealed.

The researchers observed that the polymerase manages to access the RNA without separating it from the proteins that protect it. This is essential because it preserves the structure of the genome, which in turn allows it to multiply continuously. The polymerase is able to produce multiple copies from the same parental RNA in several rounds, which is a key aspect for viral multiplication.

The polymerase is capable of producing multiple copies from the same parental RNA in several rounds.

A control mechanism in viral multiplication

These nanoscopic “films” allowed researchers to estimate the rate of RNA synthesis, the speed at which the viral polymerase works. The polymerase It is capable of incorporating up to 35 nucleotides in one second. If we equate a nucleotide with a letter, a copyist working at this speed would be able to copy the first part of Don Quixote in just 6 hours (or the first Harry Potter book in 3 hours).

The team of researchers also discovered that the structure of the nascent RNA determines the speed at which the polymerase works.

The team of researchers also discovered that the structure of the nascent RNA determines the speed at which the polymerase works. The conformation of the nascent RNA therefore functions as a control mechanism that regulates the speed of amplification of the virus and could be a therapeutic target for the development of new antiviral strategies.

Viral RNA multiplies surrounded by proteins. Unlike previous work that studied the polymerase in isolation, this discovery was made in the polymerase's natural environment, within the genome and surrounded by proteins that it has to deal with and that affect the speed of final application.

The model system of this study provides direct evidence that viral proteins individual proteins can be recycled, and confirms existing theoretical models. The work has been well received by the scientific community and offers a new approach to investigate the mechanisms of viral transcription and replication in other viruses.

"If we can define the mechanisms that govern the functioning of viral proteins, we can devise methods to interfere with them and, therefore, stop viral infection."

Borja Ibarra, coordinator of the 'Manipulation of Molecular Motors' research group at the Madrid Institute for Advanced Studies in Nanoscience

The work, recently published in DHW Nano, lays the foundation for future research into the functioning of the polymerase in the context of the viral genome, something that had not been possible until now.

Reference: Diego Carlero, Shingo Fukuda, Rebeca Bocanegra, Toshio Ando, ​​Jaime Martin-Benito and Borja Ibarra. "Conformational dynamics of influenza A virus ribonucleoprotein complexes during RNA synthesis." DHW Nano. 

Source: SINC Agency

Source: IMDEA Nanociencia (Nanoscience)

Rights: Creative Commons