Apoptosis regulation by Kaposis sarcoma microRNAs

Herpesviruses are known to encode micro (mi)RNAs and to use them to regulate the expression of both viral and cellular genes. The genome of Kaposis sarcoma herpesvirus (KSHV) encodes a cluster of twelve miRNAs, which are abundantly expressed during both latency and lytic infection. Relatively few cellular targets of KSHV miRNAs are known. Here, we used a microarray expression profiling approach to analyze the transcriptome of both B lymphocytes and endothelial cells stably expressing KSHV miRNAs and monitor the changes induced by the presence of these miRNAs. We generated a list of potential cellular targets by looking for miRNA seed-match-containing transcripts that were significantly down regulated upon KSHV miRNAs expression. Interestingly, the overlap of putative targets identified in B lymphocytes and endothelial cells was minimal, suggesting a tissue-specific target-regulation by viral miRNAs. Among the putative targets, we identified caspase 3, a critical factor for the control of apoptosis, which we validated using luciferase reporter assays and western blotting. In functional assays we obtained further evidence that KSHV miRNAs indeed protect cells from apoptosis.

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Suffert G, Malterer G, Hausser J, Viiliäinen J, Fender A, Contrant M, Ivacevic T, Benes V, Gros F, Voinnet O, Zavolan M, Ojala PM, Haas JG, Pfeffer S