How long does a transfected siRNA silence target gene?

siRNAs or miRNAs can exhibit desired results from a transient transfection as early as 4 hours post-transfection, with maximal effects at 24 to 48 hours and loss of transient effect around 120 to 144 hours.  In contrast, the analysis of a plasmid DNA transfection may need to be slightly altered to allow ample time for DNA uptake, expression and efficacy of the expressed target gene (often about within 48-96 hours post-transfection).  The timing of these cellular events is often overlooked and can be generalized as a “one-size fits all” theory, not taking into account individual protein properties.