The 5′ terminal capping of heterogeneous nuclear RNA at different embryonic stages of the sea urchin

Nemer, Martin; Surrey, Saul; Ginzburg, Irith; Echols, Martin M.

doi:10.1093/nar/6.6.2307

Cited by 2 publications

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References 44 publications

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“…Developing sea urchin embryos also contain these two classes of hnRNA, as well as a third more abundant class that contains neither poly A nor oligo A (19). The relative amounts of each of these classes differ as a function of development of the embryo (20).…”

Section: Discussionmentioning

confidence: 99%

Properties of a small transcribed poly A sequence in heterogeneous nuclear RNA of HeLa cells

et al. 1979

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A class of heterogeneous nuclear RNA (hnRNA) molecules contain an internal transcribed poly A sequence of close to 25 uninterrupted AMP residues. HnRNA molecules containing this sequence are separable from those containing the large 3' terminal poly A sequence on the basis of their differential affinity for oligo dT cellulose. The fact that the transcribed small poly A and the 3' terminal poly A are not found in the same hnRNA molecules even though both are present in similar size classes and that the small poly A is absent from cytoplasmic messenger RNA (mRNA) has led us to propose a scheme for mRNA processing in which the 3' end of the small poly A in hnRNA becomes a priming size for the post-transcriptional addiction of the large poly A.

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Section: Discussionmentioning

confidence: 99%

Properties of a small transcribed poly A sequence in heterogeneous nuclear RNA of HeLa cells

et al. 1979

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Rates of synthesis and turnover of 5′ cap structures of hnRNA and mRNA and their changes during sea urchin development

et al. 1979

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The relationship between heterogeneous nuclear RNA (hnRNA) and messenger RNA (mRNA) synthesis has been studied as a function of the development of the sea urchin embryo through the use of methyl incorporation. Several parameters in the metabolism of capped hnRNA and mRNA of early blastula and late gastrula stages have been investigated by measurin,g the kinetics of transfer of methyl groups from S-adenosylmethionine t o the 5 cap structures in nuclear and cytoplasmic RNA:1) The rate constants for the decay of hnRNA caps and the synthesis of mRNA caps are equal t o within experimental error. This equality indicates a flux of precursor hnRNA caps to mRNA caps with a very high degree of conservation of the hnRNA caps. This conservation holds for each embryonic stage.2 ) From literature data on the labeling kinetics of GTP and mRNA, we have calculated the decay constant of a putative mRNA precursor component of hnRNA. The value of this constant is very close t o that for the decay constant of hnRNA caps. Hence, all hnRNA caps and some portion of their associated hnRNA sequences behave kinetically as the pre-mRNA fraction. This kinetically ascribed pre-mRNA comprises approximately 30% of the hnRNA mass.3) The part of the hnRNA which does not serve as precursor t o mRNA turns over at least twice as rapidly as the pre-mRNA fraction. 4) During development from early blastula to late gastrula, the rate of hnRNA cap synthesis drops from 2 X 1 O3 molecules/min/cell to half of this value. This decline is parallel t o the decline in total hnRNA synthesis and thereby confirms the constant degree of capping of hnRNA, as previously reported. We infer that the pre-mRNA fraction of hnRNA remains nearly constant during this developmental period. [6] as well as sets of single-copy sequences [ 7 ] . Hence, changes in the production of mRNA appear to involve transcriptional and, to a larger extent, posttranscriptional processes. To d understand the regulation of niRNA synthesis as a function of embryonic development, it is important t o study the relationship between hnRNA and mRNA synthesis, determine the nature of the fraction of hnRNA which is pre-mRNA and whether or not this fraction changes quantitatively during development,The generation of mRNA molecules from eukaryotic transcripts is now seen to be complicated by the conservation, splicing and ligating of selected sequences [8-151 . In order t o evaluate the relationship between entire hnRNA and mRNA populations, the use of a general reference structure common to these molecules appears to be required. The 5' terminal cap may be taken as such a structure, because almost all mRNA molecules are characteristically capped, as shown in mammalian cells [ 16, 171 and sea urchin embryos [18]. Furthermore, the 5' cap structure may be strictly characteristic of premRNA if, as demonstrated in mouse L-cell fibroblasts [19] , hnRNA caps are conserved in the processing to form capped mRNA. In the present study we have measured the rate constants for the synthesis and decay of hnRNA cap...

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The 5′ terminal capping of heterogeneous nuclear RNA at different embryonic stages of the sea urchin

Cited by 2 publications

References 44 publications

Properties of a small transcribed poly A sequence in heterogeneous nuclear RNA of HeLa cells

Properties of a small transcribed poly A sequence in heterogeneous nuclear RNA of HeLa cells

Rates of synthesis and turnover of 5′ cap structures of hnRNA and mRNA and their changes during sea urchin development

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