3' UTR seed matches, but not overall identity, are associated with RNAi off-targets

Off-target gene silencing can present a notable challenge in the interpretation of data from large-scale RNA interference (RNAi) screens. We performed a detailed analysis of off-targeted genes identified by expression profiling of human cells transfected with small interfering RNA (siRNA). Contrary to common assumption, analysis of the subsequent off-target gene database showed that overall identity makes little or no contribution to determining whether the expression of a particular gene will be affected by a given siRNA, except for near-perfect matches. Instead, off-targeting is associated with the presence of one or more perfect 3' untranslated region (UTR) matches with the hexamer or heptamer seed region (positions 2-7 or 2-8) of the antisense strand of the siRNA. These findings have strong implications for future siRNA design and the application of RNAi in high-throughput screening and therapeutic development.     

Effect of some polypeptide hormones on the lateral mobility in plasma membranes of rat testes, L-cells and liver. Influence of development and ageing

1. The effect of different doses of six polypeptide hormones on pyrene diffusion in rat testes and liver plasma membranes was tested. Pyrene mobility was reduced in membranes possessing respective receptors. 2. An incubation time of 15 min of testes plasma membranes with 10(-5) M lutropin (LH) reduced pyrene and diphenyl hexatriene mobilities by 10-20%. 3. The addition of 10(-5) M LH to a suspension of intact L-cells from rats at different ages decreased the diffusion of membrane fluorescently labelled lipids and proteins by ca 60%. Diffusion was measured by fluorescence recovery after photobleaching. 4. Observed LH effects were independent of development and ageing.