sentences:  It also synthesizes long, highly heteropolymeric tails "in vivo".It accounts for all of the observed residual polyadenylation in strains of "Escherichia coli" missing the normal polyadenylation enzyme.Discovered by Marianne Grunberg-Manago working in Severo Ochoa's lab in 1955, the RNA-polymerization activity of PNPase was initially believed to be responsible for DNA-dependent synthesis of messenger RNA, a notion that got disproved by the late 1950s.