Key result
Mammalian cells degrade 90% of heterogeneous nuclear RNA within minutes, leaving little for cytoplasmic mRNA.
Why the study?
The synthesis and rapid turnover of a large fraction of nucleoplasmic RNA and the transport of only a small fraction to the cytoplasm in mammalian cells was not well understood.
Describes polydisperse nuclear RNA in mammalian cells; leaves open mechanisms of selective mRNA transport and processing.
One puzzle of RNA metabolism in mammalian cells has been the synthesis and rapid turnover of a large fraction of nucleoplasms RNA with the transport to the cytoplasm of only a small fraction of the total synthesized material (Scherrer et al. 1963; Harris and Watts 1962). This rapidly labeled nuclear RNA fraction is polydisperse in length, has a base composition similar to that of total cell DNA, and is significantly longer than cytoplasmic mRNA. Thus, this RNA fraction has been referred to as heterogeneous nuclear RNA (hnRNA) (Soeiro et al. 1966, 1968). Several laboratories have studied the stability of hnRNA and have concluded that 90% of it is degraded in the nucleus within minutes (Soeiro et al. 1968; Brandhorst and McConkey 1974). Since only a small fraction of the total RNA synthesized in a mammalian cell becomes mRNA and since nucleotide triphosphate pools are large, it has not been possible...
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Berget et al. (1978) studied RNA metabolism in mammalian cells. In mammalian cells, 90% of heterogeneous nuclear RNA is degraded in the nucleus within minutes, with only a small fraction becoming cytoplasmic mRNA.
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