Decoupling of HSV1 Vhs protein mRNA decay and translation stimulation functions
Metadata[+] Show full item record
Herpes Simplex Virus Type 1 is a member of the alphaherpesvirinae subfamily within the family Herpesviridae. This virus has both a lytic and latent cycle. Primary infection occurs when the virus enters epithelial cells around the mucosal lining of the nose and mouth. Within the epithelial cells, the virus undergoes an active lytic infection, causing an ulcerated blister, more famously known as a 'cold sore' or 'fever blister'. Once HSV enters the nearby sensory neurons the genome is transported to the neuronal cell body where its latency associated transcripts are activated and the virus remains in a dormant latent cycle until reactivation, when the virus is transported back down the axon to the epithelial cells at or near the site of initial infection. The Virion Host Shutoff protein is a tegument protein from HSV1 and acts as a ribonuclease, degrading both cellular and viral mRNAs, making the course of viral infection more efficient. A study by Saffran, Read and Smiley uncovered an unexpected new function of Vhs: stimulation of translation from some IRESs. An IRES is a section of mRNA with a high level of secondary structure, capable of inducing cap-independent translation. In similar experiments utilizing a bicistronic reporter transcript, I sought to discover whether or not these two functions of the Vhs protein could be de-coupled. Experiments involved dually transfecting HeLa cells with different Vhs mutants across a range of Vhs plasmid concentrations and the bicistronic reporter construct. Levels of reporter activity were measured from cell lysates 36 hours after transfections and provided a measurement of the control at the level of translation. As the cellular Bip IRES element was present between the cistrons, the 3' cistron provided a measure of IRES stimulation. The Results revealed examples of Vhs mutants in which the two activities had been separated. It is unknown what role IRES stimulation could play during Herpesvirus infection, although it is interesting to note that some HSV1 genes have IRES like elements within the 5' UTR. Future experiments can be done to investigate whether or not Vhs is actively recruiting transcription initiation factors to these IRES elements.
Table of Contents
Introduction -- Materials and methods -- Results and discussion