Expression of cellular genes in CD4 positive lymphoid cells infected by the human immunodeficiency virus, HIV-1: Evidence for a host protein synthesis shut-off induced by cellular mRNA degradation

Abstract

We have investigated the effects of HIV-1 infection on cellular gene expression in two different human CD4 positive lymphoid cell lines: CEM and C8166 cells. As a prerequisite for this study it was necessary to develop virus-cell culture systems in which >90% of the cells could be near synchronously infected by HIV-1. Further, since HIV-1 is a cytopathic virus, it was essential that cellular gene expression be examined in virus-infected cells which remained viable. After meeting these requirements, we measured cellular RNA and protein levels in virus-infected lymphocytes. In the cell lines examined the levels of cellular protein synthesis markedly decreased at times when viral-specific protein synthesis was increasing. Both Northern and slot blot analysis revealed that the declines in host protein synthesis were due, at least in part, to declines in steady state levels of cellular mRNAs. Runoff assays with nuclei isolated from infected cells demonstrated that the decreases in cellular mRNA levels were not due to declines in cellular RNA polymerase II transcription rates. To determine if the decreases in cellular protein synthesis also might be due to specific translational controls exerted by HIV-1, we compared the polysome association of cellular RNAs in infected and uninfected C8166 cells. The polysome distribution of cellular mRNAs was virtually identical in mock- and HIV-1-infected cells although, as expected, the total amount of cellular mRNAs were significantly lower in virus-infected cells. Taken together, these results suggest that HIV-1 may encode mechanisms to inhibit cellular protein synthesis, likely as a result of cellular mRNA degradation, rather than specific blocks in cellular mRNA translation.