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Small nuclear ribonucleoproteins and heterogeneous nuclear ribonucleoproteins in the amphibian germinal vesicle: loops, spheres, and snurposomes.
J Cell Biol 1991; 113(3):465-83JC

Abstract

We have examined the distribution of snRNPs in the germinal vesicle (GV) of frogs and salamanders by immunofluorescent staining and in situ nucleic acid hybridization. The major snRNAs involved in pre-mRNA splicing (U1, U2, U4, U5, and U6) occur together in nearly all loops of the lampbrush chromosomes, and in hundreds to thousands of small granules (1-4 microns diameter) suspended in the nucleoplasm. The loops and granules also contain several antigens that are regularly associated with snRNAs or spliceosomes (the Sm antigen, U1- and U2-specific antigens, and the splicing factor SC35). A second type of granule, often distinguishable by morphology, contains only U1 snRNA and associated antigens. We propose the term "snurposome" to describe the granules that contain snRNPs ("snurps"). Those that contain only U1 snRNA are A snurposomes, whereas those that contain all the splicing snRNAs are B snurposomes. GVs contain a third type of snRNP granule, which we call the C snurposome. C snurposomes range in size from less than 1 micron to giant structures greater than 20 microns in diameter. Usually, although not invariably, they have B snurposomes on their surface. They may also contain from one to hundreds of inclusions. Because of their remarkably spherical shape, C snurposomes with their associated B snurposomes have long been referred to as spheres or sphere organelles. Most spheres are free in the nucleoplasm, but a few are attached to chromosomes at specific chromosome loci, the sphere organizers (SOs). The relationship of sphere organelles to other snRNP-containing structures in the GV is obscure. We show by immunofluorescent staining that the lampbrush loops and B snurposomes also react with antibodies against heterogeneous nuclear ribonucleoproteins (hnRNPs). Transcription units on the loops are uniformly stained by anti-hnRNP and anti-snRNP antibodies, suggesting that nascent transcripts are associated with hnRNPs and snRNPs along their entire length, perhaps in the form of a unitary hnRNP/snRNP particle. That B snurposomes contain so many components involved in pre-mRNA packaging and processing suggests that they may serve as sites for assembly and storage of hnRNP/snRNP complexes destined for transport to the nascent transcripts on the lampbrush chromosome loops.

Authors+Show Affiliations

Department of Embryology, Carnegie Institution, Baltimore, Maryland 21210.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

1826687

Citation

Wu, Z A., et al. "Small Nuclear Ribonucleoproteins and Heterogeneous Nuclear Ribonucleoproteins in the Amphibian Germinal Vesicle: Loops, Spheres, and Snurposomes." The Journal of Cell Biology, vol. 113, no. 3, 1991, pp. 465-83.
Wu ZA, Murphy C, Callan HG, et al. Small nuclear ribonucleoproteins and heterogeneous nuclear ribonucleoproteins in the amphibian germinal vesicle: loops, spheres, and snurposomes. J Cell Biol. 1991;113(3):465-83.
Wu, Z. A., Murphy, C., Callan, H. G., & Gall, J. G. (1991). Small nuclear ribonucleoproteins and heterogeneous nuclear ribonucleoproteins in the amphibian germinal vesicle: loops, spheres, and snurposomes. The Journal of Cell Biology, 113(3), pp. 465-83.
Wu ZA, et al. Small Nuclear Ribonucleoproteins and Heterogeneous Nuclear Ribonucleoproteins in the Amphibian Germinal Vesicle: Loops, Spheres, and Snurposomes. J Cell Biol. 1991;113(3):465-83. PubMed PMID: 1826687.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Small nuclear ribonucleoproteins and heterogeneous nuclear ribonucleoproteins in the amphibian germinal vesicle: loops, spheres, and snurposomes. AU - Wu,Z A, AU - Murphy,C, AU - Callan,H G, AU - Gall,J G, PY - 1991/5/1/pubmed PY - 1991/5/1/medline PY - 1991/5/1/entrez SP - 465 EP - 83 JF - The Journal of cell biology JO - J. Cell Biol. VL - 113 IS - 3 N2 - We have examined the distribution of snRNPs in the germinal vesicle (GV) of frogs and salamanders by immunofluorescent staining and in situ nucleic acid hybridization. The major snRNAs involved in pre-mRNA splicing (U1, U2, U4, U5, and U6) occur together in nearly all loops of the lampbrush chromosomes, and in hundreds to thousands of small granules (1-4 microns diameter) suspended in the nucleoplasm. The loops and granules also contain several antigens that are regularly associated with snRNAs or spliceosomes (the Sm antigen, U1- and U2-specific antigens, and the splicing factor SC35). A second type of granule, often distinguishable by morphology, contains only U1 snRNA and associated antigens. We propose the term "snurposome" to describe the granules that contain snRNPs ("snurps"). Those that contain only U1 snRNA are A snurposomes, whereas those that contain all the splicing snRNAs are B snurposomes. GVs contain a third type of snRNP granule, which we call the C snurposome. C snurposomes range in size from less than 1 micron to giant structures greater than 20 microns in diameter. Usually, although not invariably, they have B snurposomes on their surface. They may also contain from one to hundreds of inclusions. Because of their remarkably spherical shape, C snurposomes with their associated B snurposomes have long been referred to as spheres or sphere organelles. Most spheres are free in the nucleoplasm, but a few are attached to chromosomes at specific chromosome loci, the sphere organizers (SOs). The relationship of sphere organelles to other snRNP-containing structures in the GV is obscure. We show by immunofluorescent staining that the lampbrush loops and B snurposomes also react with antibodies against heterogeneous nuclear ribonucleoproteins (hnRNPs). Transcription units on the loops are uniformly stained by anti-hnRNP and anti-snRNP antibodies, suggesting that nascent transcripts are associated with hnRNPs and snRNPs along their entire length, perhaps in the form of a unitary hnRNP/snRNP particle. That B snurposomes contain so many components involved in pre-mRNA packaging and processing suggests that they may serve as sites for assembly and storage of hnRNP/snRNP complexes destined for transport to the nascent transcripts on the lampbrush chromosome loops. SN - 0021-9525 UR - https://www.unboundmedicine.com/medline/citation/1826687/Small_nuclear_ribonucleoproteins_and_heterogeneous_nuclear_ribonucleoproteins_in_the_amphibian_germinal_vesicle:_loops,_spheres,_and_snurposomes L2 - http://jcb.rupress.org/cgi/pmidlookup?view=long&pmid=1826687 DB - PRIME DP - Unbound Medicine ER -