Half-life of Escherichia coli polyadenylated lipoprotein mRNA.

In the light of recent evidence that the half-life of bacterial mRNA may be modulated by polyadenylation at the 3' end, we determined the half-life of polyadenylated lpp mRNA, which is an abundant and comparatively stable message encoding a major lipoprotein of the outer membrane. Messenger RNAs were pulse-labeled with [3H] adenosine and poly(A) RNA was isolated at various times after pulse-labeling by affinity chromatography on oligo(dT) cellulose. The amount of lpp mRNA remaining was quantitated by hybridization with the antisense strand of the lpp gene cloned in M13mp18. The observed half-life for polyadenylated lpp mRNA was 12 min. This represents the first half-life measurement for a specific polyadenylated mRNA in E. coli, and is slightly longer than the half-life of total lpp RNA reported earlier. It coincides with the functional half-life for lpp mRNA determined by Inouye and coworkers by measuring the rate of lipoprotein synthesis at various times after rifampicin addition. This suggest that polyadenylated lpp RNA is the predominant and translationally active form of lpp mRNA within the cell.