Plasmids were linearized by BamHI and purified by phenol/ chloroform extraction followed by ethanol precipitation. In vitro transcription was conducted by SP6 RNA polymerase and carried out in the 30 ml reaction mixture of: 1 mg of linearized template, 5 mM of rNTPs, 20 units of RNase inhibitor and 15 units of SP6 RNA polymerase with buffer (all from Promega, Benelux). After 2 h incubation at 37 C, the integrity and quantity of transcripts were checked by agarose gel and appropriate amount of the RNA were diluted in nuclease free water for in vitro translation.