Shortening of the poly(A) region of mouse globin messenger RNA.

Poly(adenylic acid) degradation by two distinct processes in the cytoplasmic RNA of Physarum polycephalum

“…The poly(A) shortening process which we have described in Physarum cytoplasmic RNA probably entails the gradual erosion of this sequence from its 3' terminus in a similar fashion to that previously described in mammalian cells (Brawerman, 1973;Sheiness & Darnell, 1973;Merkel et al, 1976) and other lower eukaryotes (Jaworski et al, 1976;Freer et al, 1977). Furthermore, in Physarum, like in mammalian cells (Sheiness & Darnell, 1973;Jeffery & Brawerman, 1974;Brawerman & Diez, 1975), the shortening process does not completely destroy the poly(A) sequence since tracts consisting of about 50 nucleotide residues remain in the steady-state RNA and accumulate when the poly(A) turnover process is suppressed by cycloheximide.…”

“…The cycloheximide-induced stabilization of poly(A) is clearly not a result of interference with the synthesis of a nuclease which normally catalyzes degradation since this phenomenon is not seen when protein synthesis is blocked by heat shock. In contrast to the turnover process, the Physarum poly(A) shortening process, like that observed in other eukaryotic cells (Brawerman, 1973;Merkel et al, 1976;Dworkin et al, 1977) does not appear to be linked to translation since it can be carried out when poly( A) + RNA is incorporated into polysomes or free cytoplasmic ribonucleoprotein. These findings are consistent with the possibility that poly(A) shortening is caused by a component integrated within the mRNP structure whereas the factor responsible for the turnover process might be transiently associated with the mRNA involved in translation.…”

Messenger ribonucleic acid metabolism in mammalian mitochondria: relationship between the decay of mitochondrial mRNA and their poly(A)

“…Fragments. It is well known that the cytoplasmic poly(A) shortens progressively when pulse-labeled cells are chased either with actinomycin D or with unlabeled medium (Sheiness & Darnell, 1973; Sheiness et al, 1975;Merkel et al, 1976). Since there is no such information on the metabolic degradation of mitochondrial poly (A), it was decided to analyze the size distribution of mitochondrial poly(A) during a pulsechase.…”

Length of the polyadenylated sequence in cytoplasmic ribonucleic acid isolated from fetal calf myoblasts differentiating in vitro

“…In muscle cells, after 3 h labeling, the poly(A) distribution is still predominantly in a mode which differs from that of the steady state. Values obtained, for example, with reticulocytes, where aging is estimated over a 9-12-h labeling period, may still be influenced by initial processing (Merkel et al, 1976;Nokin et al, 1976). Results with adenovirus-infected cells would suggest that the rapidity with which the poly(A) tract is shortened is correlated with the half-life of the messenger RNA (Williamson et al, 1974).…”

“…Actual degradation of messenger RNA apparently takes place (Marbaix et al, 1975;Huez et al, 1977), although Doel & Carey (1976) have claimed that in the case of the translation of ovalbumin messenger RNA in a reticulocyte lysate, reduction in poly(A) chain length results in reduced efficiency of translation, but no messenger degradation. Some in vivo experiments with inhibitors of protein synthesis suggest that there is an association between translation and shortening of poly(A) chain length (Sheiness et al, 1975), while others do not (Merkel et al, 1976). Adams & Jeffery (1978) have suggested that the turnover rather than the shortening of poly(A) may be linked with the translation cycle.…”