Highlights from the article: Total RNAs prepared from exponentially growing or stationary-phase I E. coli i cells were used for primer extension analysis (Figure). P3 was highly active in the mid-exponential phase (5 h growth), but its activity sharply decreased when cells entered the stationary phase. For identification of 5' ends of I cnu i mRNA, total cellular RNA was analyzed by primer extension using primer Ext (5' GAA CTG ATT TTG CGA AAT TTT AAT AAG TAG TCC 3'), as previously described.[8] Briefly, the primer was 5'-end-labeled with [ - SP 32 sp P]ATP and T4 polynucleotide kinase.