Poly(A)‐Containing RNA in Neuroblastoma: Immature and Differentiated Cells in Culture

Abstract

We have analysed the poly(A)‐containing RNA from neuroblastoma cells at two different developmental states: either as round, immature neuroblasts grown in suspension, or as differentiated cells exhibiting the morphological properties of mature neurons, when attached to a culture dish. Suspension‐grown and monolayer cells were pulse‐labelled with tritiated uridine. The profile of cytoplasmic poly(A)‐containing RNA from suspension cells is highly heterogeneous with peaks ranging from 16–30 S. The profile obtained from differentiated cells appears somewhat distinct from the previous one. This is evidenced by a relative decrease in the 26‐S peak and a virtual disappearance of the 16‐S component. In order to compare the ‘steady‐state’ patterns of poly(A)‐containing RNA in these two developmental stages, polysomal RNA was prepared from unlabelled cells. Following sucrose gradient sedimentation, each fraction was hybridized to [³H]poly(U). Examination of the two RNA hybridization profiles reveals striking similarities suggesting that ‘steady‐state’ messenger populations include, on the average, the same subspecies. The 16‐S fraction, which was not observed after the pulse‐labelling of the monolayer culture, is detected here by hybridization to [³H]poly(U) when using polysomal poly(A)‐containing RNA from monolayer cells as substrate. These results suggest that terminal differentiation of neuroblastoma cells is not accompanied by major alterations of the transcription program and is paralleled by a marked stabilization of the 16‐S species.