Plasmid DNAs were prepared using the Qiagen mini-prep kits and were linearized with DraI in a total volume of 20 ml. Proteins were eliminated by the addition of 2 ml of 1 mg/ml proteinase K and SDS to a final concentration of 0.5% followed by digestion at 50 C for 30 min. Volumes were then increased to 100 ml, extracted twice with phenol/chloroform, and DNA was precipitated with 10 ml NH 4 Ac and 250 ml ethanol. The purified DNA was resuspended in DEPCtreated H 2 O. To prepare synthetic mRNAs, 2 ml of purified linear DNAs were used for in vitro transcription using the Ambion T7 mMachine mMessage kit. RNAs were precipitated using 30 ml DEPC H 2 O and 25 ml LiAc. The RNA was resuspended in 11 ml DEPC H 2 O (1 ml in 500 would give an OD 260 of 0.05-00.1; 1-2 mg/ml).