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

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

Hormone-dependent dissociation of blood flow and secretion rate in the lingual salt glands of the estuarine crocodile, Crocodylus porosus

Salt and water balance in the estuarine crocodile, Crocodylus porosus, involves the coordinated action of both renal and extra-renal tissues. The highly vascularised, lingual salt glands of C. porosus excrete a concentrated sodium chloride solution. In the present study, we examined the in vivo actions of vasoactive intestinal peptide (VIP), B-type natriuretic peptide (BNP) and angiotensin II (ANG II) on the secretion rate and blood perfusion of the lingual salt glands. These peptides were selected for their vasoactive properties in addition to their reported actions on salt gland activity in birds and turtles and rectal gland activity in elasmobranchs. The femoral artery was cannulated in seven juvenile crocodiles for delivery of peptides and measurement of mean blood pressure and heart rate. In addition, secretion rate of, and blood flow to, the salt glands were recorded simultaneously using laser Doppler flowmetry. VIP stimulated salt secretion was coupled to an increase in blood flow and vascular conductance of the lingual salt glands. BNP was a potent stimulant of salt gland secretion, resulting in a maximal secretion rate of more than 15-fold higher than baseline; however, this was not coupled to an increase in perfusion rate, which remained unchanged. ANG II failed to stimulate salt gland secretion and there was a transient decrease in salt gland blood flow and vascular conductance. It is evident from this study that blood flow to, and secretion rate from, the lingual salt glands of C. porosus are regulated independently; indeed, it is apparent that maximal secretion from the salt glands may not require maximal blood flow