Human Cytomegalovirus Infection Alters the Expression of Cellular MicroRNA Species That Affect Its Replication

Abstract

The human genome encodes over 500 microRNAs (miRNAs), small RNAs (19 to 26 nucleotides [nt]) that regulate the expressions of diverse cellular genes. Many cellular processes are altered through a variety of mechanisms by human cytomegalovirus (HCMV) infection. We asked whether HCMV infection leads to changes in the expression of cellular miRNAs and whether HCMV-regulated miRNAs are important for HCMV replication. Levels of most miRNAs did not change markedly during infection, but some were positively or negatively regulated. Patterns of miRNA expression were linked to the time course of infection. Some similarly reregulated miRNAs share identical or similar seed sequences, suggesting coordinated regulation of miRNA species that have shared targets. miRNAs miR-100 and miR-101 were chosen for further analyses based on their reproducible changes in expression after infection and on the basis of having predicted targets in the 3 untranslated regions (3-UTR) of genes encoding components of the mammalian target of rapamycin (mTOR) pathway, which is important during HCMV infection. Reporter genes that contain the 3-UTR of mTOR (predicted targets for miR-100 and miR-101) or raptor (a component of the mTOR pathway; predicted site for miR-100) were constructed. Mimics of miR-100 and miR-101 inhibited expression from the mTOR construct, while only miR-100 inhibited the raptor construct. Together, miR-100 and miR-101 reduced mTOR protein levels. While the miR-100 and miR-101 mimics individually modestly inhibited production of infectious progeny, much greater inhibition was achieved with a combination of both (33-fold). Our key finding is that HCMV selectively manipulates the expression of some cellular miRNAs to help its own replication.MicroRNAs (miRNAs) are small (ϳ21-nucleotide [nt]) RNA species that are expressed from specialized genes and have important roles in the regulation of cellular gene expression, including the regulation of development, the differentiation of hematopoietic stem cells, apoptosis, and the development of cancer (reviewed in references 16, 25, and 26

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The Cell Biology of Cytomegalovirus: Implications for Transplantation

“…This tissue specificity suggests that CMV may activate multiple transcriptional programs depending on the The mechanisms underlying tissue specificity of viral gene expression may also relate to recently described and generally conserved microRNAs (miRNAs) of CMV (77)(78)(79)(80)(81). These small, noncoding RNA species have diverse effects including regulation of viral replication and immune evasion, which appear to vary by the cell type infected (77)(78)(79)(80)(81)(82)(83). HCMV-miR-UL112-3p, for example, appears to affect both the stress-induced ligand MICB and the antiviral interferon-response element IRF-1 (80,84).…”