transcript expression evidence primer extension assay evidence swolfish eco The primer extension assay (Fig. 6a) defined the transcription start sites the three sRNA genes qrr2 - 4, and this assay also indicated that the promoter activity of all the thee qrr genes was under the positive control of OpaR. The most commonly used radiolabel is 32P. CollecTF A type of transcript expression evidence used to determine expression levels of mRNA where a labeled synthetic oligonucleotide primer is annealed to mRNA downstream of the presumed transcription start site of a gene. The mRNA is extended with reverse transcriptase, producing cDNA which is electrophoresed, and the band size is enables determination of the 5' end of the mRNA (i.e. the transcription start site). The primer extension assay detected two transcriptional start sites located at 343 and 78 bp upstream of rovA (Fig. 2); therefore, two promoters (named P2 and P1, respectively) were transcribed for rovA. ECO:0001819 2015-11-04T09:33:18Z