schematic of T7 expression system (IMAGE) DOE/Brookhaven National Laboratory Caption Studier's T7 expression system uses the T7 promoter to "turn on" a gene of interest and the T7 RNA polymerase to transcribe that gene into messenger RNA (mRNA) so that E. coli ribosomes can use the RNA-encoded information to synthesize the desired protein. The system can also be used to make desired mRNAs as, for example, was done to make the COVID-19 mRNA vaccines. Credit Tiffany Bowman/Brookhaven National Laboratory Usage Restrictions OK for use in stories about this work. License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.