RNA metabolism in M1 adrenergic neuroblastoma cells

Hybridization studies of poly A-RNA from 5'-bromodeoxyuridine treated neuroblastoma cells

Hybridization studies were carried out to measure sequence complexity and relative complexity of poly A-RNA populations from M1 neuroblastoma cells cultivated under proliferating conditions and after BrdU treatment. BrdU treatment is known to induce morphological differentiation. Hybridization kinetics were performed with [3H] labelled complementary DNA synthetized by reverse transcriptase action. The total complexities and the complexities of three classes of sequences measured for the two developmental states differed significantly. In particular, the total complexities as well as the complexity of the rare sequences class were higher in the poly A-RNA population of morphological differentiated M1 cells. Heterologous hybridization between poly A-RNA of proliferating cells with cDNA of differentiated M1 cells was very close to the homologous hybridization of poly A-RNA and cDNA from differentiated cells, nevertheless significant differences, were found in the intermediate and in the rare sequences classes. On the other hand the inverse heterologous hybridization (poly A-RNA of differentiated state X cDNA of proliferating cells) showed a lower hybridization in the region of Rot higher than 1. The plateau reached only 87 per cent compared to that of the homologous hybridization, suggesting that certain sequences expressed in the differentiated state. Nevertheless the number of different poly A-RNA species present per cell (seen by homologous hybridization experiments) was higher in differentiated state indicating that selective transcription took place beside repression with morphological differentiation.

In vitro protein synthesis activity of poly(A) RNA from neuroblastoma cells

Protein synthesis activity of poly(A) RNA from M1 neuroblastoma cells was studied in a reticulocyte cell-free system. The activity of poly(A) RNA from M1 cells "differentiated" morphologically by bromodeoxyuridine was compared with that of proliferating cells. Poly(A) RNA from differentiated cells was about 10% more active than the corresponding RNA from proliferating cells. The products synthesized in vitro were fractionated by polyacrylamide gradient gel electrophoresis. A 420,000-dalton band was present in the translation products programmed by differentiated cell poly(A) RNA; it was absent in the translation products programmed by proliferating cell poly(A) RNA.