Association of RNA with the B and C snurposomes of Xenopus oocyte nuclei (original) (raw)

Abstract

We studied the time course of [3H]-uridine incorporation into the B and C snurposomes of Xenopus oocyte nuclei. B snurposomes constitute most of the non-nucleolar granules in the 1–4 μm size range; they contain the five splicing small nuclear RNAs (snRNAs; U1, U2, U4, U5 and U6) plus a variety of associated proteins. The organelles referred to as spheres consist of a C snurposome with one or more B snurposomes on its surface. C snurposomes can exist independently of Bs and many are smaller than the structures usually classified as spheres. C snurposomes contain the trimethylguanosine moiety characteristic of snRNAs, as well as the Sm epitope found on several small nuclear ribonucleoproteins (snRNPs), but it is not known which snRNA(s) they contain. When oocytes are incubated with [3H]uridine, all of the nucleoli and chromosome loops label strongly and rapidly. By contrast, labelled RNA appears slowly in the B snurposomes and then only in a fraction of them. After a 24 h incubation, about half of the Bs are labelled, and half are unlabelled or weakly labelled. This observation suggests that there are “mature” and “immature” B snurposomes, and that only the latter acquire newly synthesized RNA. The nature of this RNA is unknown, but it probably includes the splicing snRNAs. B snurposomes on the surface of Cs also constitute a heterogeneous population, some becoming labelled and some remaining unlabelled during a 24 h incubation. An analysis of the label in “doublets” (one B and one C snurposome) suggests that RNA may pass from the Bs to the Cs.

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Authors and Affiliations

1. Department of Embryology, Carnegie Institution of Washington, 115 West University Parkway, 21210, Baltimore, MD, USA
   Harold G. Callan & Joseph G. Gall
2. Gatty Marinc Laboratory, University of St. Andrews, KY16 8LB, St. Andrews, Fife, Scotland
   Harold G. Callan

Authors

1. Harold G. Callan
2. Joseph G. Gall

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by W. Hennig

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Callan, H.G., Gall, J.G. Association of RNA with the B and C snurposomes of Xenopus oocyte nuclei.Chromosoma 101, 69–82 (1991). https://doi.org/10.1007/BF00357056

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• Received: 22 May 1991
• Accepted: 08 June 1991
• Issue date: November 1991
• DOI: https://doi.org/10.1007/BF00357056

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