Role and Virology of RSV and RSV RNA Polymerase

Abstract

Respiratory syncytial virus (RSV) is a highly contagious, respiratory virus that commonly infects children under the age of five. RSV infections can present as cold-like symptoms which include a runny nose, coughing, and fever among other common symptoms; however, RSV can cause more severe infections such as bronchiolitis and pneumonia in young children and older, immunosuppressed patients. Despite RSV being a leading cause for respiratory illness in small children, there is limited research on its molecular biology, and especially its RNA polymerase. That being said, there has been slow progress in the development of a vaccine, partly due to the history of failed trials in the past. What is known is that the viral infection of RSV is initiated through the delivery of a virus-specific RNA synthesis machine into the host cell. This machine is responsible for both genome replication and gene transcription, thus including the RNA polymerase as a component. The RSV RNA polymerase consists of two units, a core large (L) protein, and a modulatory phosphoprotein (P). The L protein is 250 kDa with three functional domains: the RNA dependent RNA polymerization (RdRp), the capping (Cap), and the cap methyltransferase (MT) domains. As for the P protein, it has two domains that are understood to be the Oligomerization domain (POD) and the C-terminal domain (PPTD). These two domains are known to interact with the RdRp and Cap domains of the L protein which is essential in stabilizing the structure of the overall protein. The L protein serves as the core of the RSV structure and is responsible for the catalyzation of the RNA polymerization in replication and transcription, the cap addition, and cap methylation of nascent viral mRNAs. When synthesizing RNA, RSV RNA uses the nucleoprotein coated genomic RNA (N:RNA) as the template. In this process, the L protein requires the tetrameric P protein to displace the nucleoproteins. The synthesis of the mRNA caps first begins when a polyribonucleotide transferase forms the mRNA caps. This is a notable distinction from eukaryotes and other viral families which use guanylyltransferase instead. The caps are then methylated by the RNA polymerase at the 2’-O position, followed by the N-7 position, a pattern opposite from the order followed in mammalian mRNA. The refined mechanisms of these processes have yet to be described, but it is speculated that they share similarities with the cap addition and methylation assays of vesicular stomatitis virus (VSV), whose assays have been reported. The Walton High School MAPS team worked in partnership with the MSOE Center for Biomolecular Modeling to design a 3D model of RSV RNA Polymerase using a recently published cryo-electron microscopy structure to further investigate and examine the structure-function relationship of RSV RNA polymerase.