HTLV-1 Tax Mediated Downregulation of miRNAs Associated with Chromatin Remodeling Factors in T Cells with Stably Integrated Viral Promoter

Abstract

RNA interference (RNAi) is a natural cellular mechanism to silence gene expression and is predominantly mediated by microRNAs (miRNAs) that target messenger RNA. Viruses can manipulate the cellular processes necessary for their replication by targeting the host RNAi machinery. This study explores the effect of human T-cell leukemia virus type 1 (HTLV-1) transactivating protein Tax on the RNAi pathway in the context of a chromosomally integrated viral long terminal repeat (LTR) using a CD4 + T-cell line, Jurkat. Transcription factor profiling of the HTLV-1 LTR stably integrated T-cell clone transfected with Tax demonstrates increased activation of substrates and factors associated with chromatin remodeling complexes. Using a miRNA microarray and bioinformatics experimental approach, Tax was also shown to downregulate the expression of miRNAs associated with the translational regulation of factors required for chromatin remodeling. These observations were validated with selected miRNAs and an HTLV-1 infected T cells line, MT-2. miR-149 and miR-873 were found to be capable of directly targeting p300 and p/CAF, chromatin remodeling factors known to play critical role in HTLV-1 pathogenesis. Overall, these results are first in line establishing HTLV-1/Tax-miRNA-chromatin concept and open new avenues toward understanding retroviral latency and/or replication in a given cell type.

HTLV-1 bZIP Factor HBZ Promotes Cell Proliferation and Genetic Instability by Activating OncomiRs

“…For example, miR181 modulates the T-cell antigen receptor sensitivity (44); miR150 regulates the transcription factor c-Myb13 and miR155 affects the differentiation of CD4 þ T lymphocytes into T helper type I (Th1) cells, regulatory T-cell development (45,46), and the promotion of T-cell-dependent tissue inflammation (46). HTLV-1 was previously shown to modify the pattern of miRNA expression in cell lines and ATLL samples (30)(31)(32)(33)(47)(48)(49)(50). Our results here add to these findings, as the miRNA expression profile of nonimmortalized infected T cells derived from carriers without malignancies was significantly distinct from that of uninfected cells.…”

“…By targeting Drosha to the proteasome, Tax influences global miRNA biogenesis (49). Furthermore, Tax activates the transcription of miR130b (33) and miR146a (32), and downregulates miR149 and miR873, which both directly target the chromatin-remodeling factors p300 and p/CAF that are known to play a critical role in HTLV-1 pathogenesis (47). Nonimmortalized HTLV-1-positive clones express a wide range of Tax RNA levels, likely modifying numerous cellular pathways (5)(6)(7)(8).…”

Human T-lymphotropic Virus Type 1-infected Cells Secrete Exosomes That Contain Tax Protein

“…Purity of the cells was confirmed by flow cytometry, and 3 ϫ 10 5 myeloid dendritic cells were cultured in 0.5 ml of AIM-V medium (Invitrogen) in a 24-well plate and either left untreated or treated with exosomes from C81, CEM, and ED(Ϫ) cells (5 g of total protein) for 48 h. Cell-free Tax was also included at (50 nM) as per previously published studies (56, 66 -68). Culture supernatants from triplicate sample sets were used to measure the concentration (pg/ml) of a panel of 12 cytokines (IL-2, IL-4, IL-5, IL-6, IL-10, IL-12, IL-13, IL-17A, IFN-␥, TNF-␣, G-CSF, and TGF-␤1) using a human Th1/Th2/ Th17 cytokine multianalyte ELISArray according to the manufacturer's protocol (SABiosciences, Frederick, MD) and as described (69).…”

Exploring the role of human miRNAs in virus–host interactions using systematic overlap analysis

“…There are many other patterns involving virus-host interactions that need to be further investigated. For example, human miRNAs can directly target viral genomes for defense (Lecellier et al, 2005), and viral proteins were also found to regulate expression of human miRNAs that targeted host chromatin remodeling proteins (Rahman et al, 2012).…”