Changes in the MicroRNA Expression Pattern Contribute to HIV-1 Tat-mediated Protection against Apoptosis and Impaired Cell Proliferation in CD4+ T Cells

HIV-1 infection changes the miRNA expression pattern in CD4+ T lymphocytes and its main regulator, Tat, has been appointed as an RNA silencing suppressor (RSS). Our group previously described that full-length Tat protects CD4+ T cells against FasL-mediated apoptosis and delays T-cell proliferation. Now we analyzed by microarrays and qRT-PCR the changes in the miRNA expression pattern of Jurkat cells induced by the intracellular expression of the two-exon Tat101 protein or the first-exon Tat72 in order to elucidate their role in the anti-apoptotic and anergic state exerted by Tat. It was determined that the expression of specific miRNAs such as hsa-miR-21, hsa-miR-222, hsa-miR-29a, and hsa-miR-1290 was up-regulated in Jurkat-Tat101. These miRNAs were related to the high activity of several transcription factors related to Tat such as NF-kB, SP1 and STAT3, and they repressed the expression of target mRNAs encoding proteins related to apoptosis and cell proliferation such as PTEN, PDCD4 and CDKN1B. In fact, mostly Jurkat-Tat101 showed an arrest at G2 phase and an impaired cytokinesis, resulting in giant, multilobulated nuclear cells. All these mechanisms would contribute to the role of Tat in HIV-1 immunosuppression and persistent infection, and the presence of Tat second exon would be essential. One microgram of total RNA extracted from triplicate independent samples of each Jurkat-Tat101, Jurkat-Tat72, and control cell lines was subjected to specific labeling of miRNAs using miRCURY LNA™ microRNA Hy3/Hy5 Power labeling kit (Exiqon, Vedbaek, Denmark), according to manufacturer’s instructions.