Introduction of a conserved sequence into the 5′UTR of additional transcription down-regulation expression of foreign proteins of measles virus minigenome

The noncoding sequences in the UTR between the Gene Start signal (GS) and the initial codon AUG from 25 measles virus genomes were compared. The conserved sequences 5′-U(NNNNN)5-8-3′ and 5'-(CNNNNNC)-3′ were found in the genome and the UTR of phosphoprotein (P) and Fusion (F) mRNA. These sequences were named the U-Unit and the C-Unit, respectively. These two sequences are different in the P and F mRNAs. To investigate whether these conserved sequences can be used to regulate expression of foreign proteins in additional transcription units (ATU), a series of minigenomes with various 5′ UTRs were generated. From reporter gene assays and quantitation of gene copies by qPCR, we found that the introduction of the C-unit into the 5′UTR of mRNA can down-regulate the expression of foreign proteins in additional transcription units in vivo.