The metabolism of a poly(A) minus mRNA fraction in HeLa cells (original) (raw)

About 30% of HeLa cell mRNA lacks poly(A) when labeled in the presence of different rRNA inhibitors. Our method of RNA fractionation precludes contamination of the poly(A)-mRNA with large amounts of poly(A)+ sequences. The poly(A)-species is associated with polyribosomes, has an average sedimentation value equal to or greater than poly(A)+ mRNA, and behaves like the poly(A)+ mRNA in its sensitivity to EDTA and puromycin release from polyribosomes. There is very little, if any, hybridization at Rot values characteristic of abundant RNA sequences between the poly(A)-RNA fractions from total cytoplasm or from polyribosomes and 3H-cDNA made to poly(A)+ RNA. This indicates that poly(A)-mRNA does not arise from poly(A)+ mRNA by nonadenylation, deadenylation, or degradation of random abundant mRNA sequences. The rate of accumulation of poly(A)-mRNA larger than 9s in the cytoplasm parallels the accumulation of poly(A)+ mRNA. The poly(A)-mRNA is maintained as approximately 30% of the total labeled mRNA in a short (90 min) and in a long (20 hr) time period. These data indicate that poly(A)-mRNA is not short-lived nuclear or cytoplasmic heterogeneous RNA contamination, and that the half-life of the poly(A)-mRNA may parallel that of the poly(A)+ mRNA. Cordycepin appears to almost completely (95%) inhibit poly(A)+ mRNA while only partially (60%) inhibiting the poly(A)-mRNA; The origin of the cordycepin-insensitive mRNA has not been ascertained.