Size-independent transport and retention of dsRNA. (A) dsRNA size-dependent silencing in Drosophila S2 cells expressing SID-1 (data adapted from Feinberg and Hunter 2003). Cells cotransfected with luciferase and SID-1 expressing plasmids were exposed to different concentrations of dsRNA of varying lengths and the extent of silencing was determined. The gray region (top) reflects average luciferase levels at the end of the experiment in samples treated with cycloheximide as a control for protein stability. (B) 10 ng/mL of 500 bp, 100 bp, and 50 bp dsRNA, and siRNA (internally labeled 500 bp dsRNA digested with Dicer) were added to induced and uninduced MT/sid-1 cells for 30 min. The mass of internalized dsRNA was normalized to 500 bp dsRNA. Error bars = 1 standard deviation, n = 2.
