Human cytomegalovirus (HCMV) causes life-threatening diseases in patients with poorly functioning immune systems as well as long-lasting neurological deficits in infants infected in utero. Among the many host cell factors that are needed by HCMV to replicate efficiently are small alkaline molecules called polyamines (PAs). Among their myriad activities, PAs bind to the protein synthesizing machinery in the cell. As well, they are necessary to make a protein, known as eIF5A, that is required for linking together amino acids to make certain proteins. Although it has been known for decades that the PAs are critical for HCMV to reproduce efficiently and that HCMV infection increases the intracellular concentration of PAs, the reasons why PAs are needed and the mechanisms the virus uses to ensure that there are sufficient amounts of PAs in the cells are unknown. Intriguing data emerging from studies of several host cell proteins that control the levels of PAs suggest that PAs and eIF5A might control expression of some HCMV genes, in particular a fascination one called, gpUL4. Prior studies showed that the production of gpUL4 is greatly repressed because the machinery for making it becomes trapped on the messenger RNA as a particular sequence of amino acids are being linked together. These and other results suggest that gpUL4, the function of which has been enigmatic for decades, might contribute to the control of PAs accumulation during HCMV infection. Using various HCMV mutants that affect the production of gpUL4 along with genetic and pharmacological tools for altering PA and eIF5A abundance, Aim 1 will reveal if and how PA and eIF5A alter the trapping mechanism during viral infection.
Aim 2 will first test the specific hypothesis that gpUL4, alone and during HCMV infection, regulates the concentration of PAs in the cells. Another experiment will test whether HCMV can somehow adapt to reproduce well even when PA levels are low. While these studies focus on HCMV, and especially gpUL4, the results will have broad implications for understanding control of other viral and cells genes that are likely regulated by a similar mechanism.
Small alkaline compounds called polyamines serve multiple functions for the cell and are required for efficient reproduction of some viruses, including the medically important pathogen human cytomegalovirus. This project aims to elucidate how polyamines affect production of viral genes and conversely, how the virus assures accumulation of the high amounts of polyamines it requires to grow.
