RNA interference-inducing hairpin RNAs in plants act through the viral defence pathway

RNA interference (RNAi) is widely used to silence genes in plants and animals. it operates through the degradation of target mRNA by endonuclease complexes guided by approximately 21 nucleotide (nt) short interfering RNAs (siRNAs). A similar process regulates the expression of some developmental genes through approximately 21 nt microRNAs. Plants have four types of Dicer-like (DCL) enzyme, each producing small RNAs with different functions. Here, we show that DCL2, DCL3 and DCL4 in Arabidopsis process both replicating viral RNAs and RNAi-inducing hairpin RNAs (hpRNAs) into 22-, 24- and 21 nt siRNAs, respectively, and that loss of both DCL2 and DCL4 activities is required to negate RNAi and to release the plant's repression of viral replication. We also show that hpRNAs, similar to viral infection, can engender long-distance silencing signals and that hpRNA-induced silencing is suppressed by the expression of a virus-derived suppressor protein. These findings indicate that hpRNA-mediated RNAi in plants operates through the viral defence pathway.

Dietary supplementation of vitamin E and -lipoic acid upregulates cell growth and signaling genes in rat myocardium

The efficacy of antioxidant supplementation in the prevention of cardiovascular disease appears equivocal, however the use of more potent antioxidant combinations than those traditionally used may exert a more positive effect. We have shown previously that supplementation of vitamin E and α-lipoic acid increases cardiac performance during post-ischemia reperfusion in older rats and increases Bcl-2 levels in endothelial cells. The purpose of this study was to examine the effects of vitamin E and α-lipoic acid supplementation on myocardial gene expression with a view to determine their mechanism of action. Young male rats received either a control (n=7) or vitamin E and α-lipoic acid supplemented diet (n=8) for 14 weeks. RNA from myocardial tissue was then amplified and samples were pooled within groups and competitively hybridized to 5K oligonucleotide rat microarrays. The relative expression of each gene was then compared to the control sample. Animals that received the antioxidant-supplemented diet exhibited upregulation (>1.5×) of 13 genes in the myocardium with 2 genes downregulated.� �Upregulated genes include those involved in cell growth and maintenance (LynB, Csf1r, Akt2, Tp53), cell signaling (LynB, Csf1r) and signal transduction (Pacsin2, Csf1r). Downregulated genes encode thyroid (Thrsp) and F-actin binding proteins (Nexilin).

Proinsulin is encoded by an RNA splice variant in human blood myeloid cells

Genes for peripheral tissue-restricted self-antigens are expressed in thymic and hematopoietic cells. In thymic medullary epithelial cells, self-antigen expression imposes selection on developing autoreactive T cells and regulates susceptibility to autoimmune disease in mouse models. Less is known about the role of self-antigen expression by hematopoietic cells. Here we demonstrate that one of the endocrine self-antigens expressed by human blood myeloid cells, proinsulin, is encoded by an RNA splice variant. The surface expression of immunoreactive proinsulin was significantly decreased after transfection of monocytes with small interfering RNA to proinsulin. Furthermore, analogous to proinsulin transcripts in the thymus, the abundance of the proinsulin RNA splice variant in blood cells corresponded with the length of the variable number of tandem repeats 5' of the proinsulin gene, known to be associated with type 1 diabetes susceptibility. Self-antigen expression by peripheral myeloid cells extends the umbrella of immunological self and, by analogy with the thymus, may be implicated in peripheral immune tolerance.