Splicing Speckles Are Not Reservoirs of RNA Polymerase II, but Contain an Inactive Form, Phosphorylated on Serine2Residues of the C-Terminal Domain
10.1091/mbc.e05-08-0726
Crossref journal-article
American Society for Cell Biology (ASCB)
Molecular Biology of the Cell (1076)
Abstract

“Splicing speckles” are major nuclear domains rich in components of the splicing machinery and polyA+RNA. Although speckles contain little detectable transcriptional activity, they are found preferentially associated with specific mRNA-coding genes and gene-rich R bands, and they accumulate some unspliced pre-mRNAs. RNA polymerase II transcribes mRNAs and is required for splicing, with some reports suggesting that the inactive complexes are stored in splicing speckles. Using ultrathin cryosections to improve optical resolution and preserve nuclear structure, we find that all forms of polymerase II are present, but not enriched, within speckles. Inhibition of polymerase activity shows that speckles do not act as major storage sites for inactive polymerase II complexes but that they contain a stable pool of polymerase II phosphorylated on serine2residues of the C-terminal domain, which is transcriptionally inactive and may have roles in spliceosome assembly or posttranscriptional splicing of pre-mRNAs. Paraspeckle domains lie adjacent to speckles, but little is known about their protein content or putative roles in the expression of the speckle-associated genes. We find that paraspeckles are transcriptionally inactive but contain polymerase II, which remains stably associated upon transcriptional inhibition, when paraspeckles reorganize around nucleoli in the form of caps.

Bibliography

Xie, S. Q., Martin, S., Guillot, P. V., Bentley, D. L., & Pombo, A. (2006). Splicing Speckles Are Not Reservoirs of RNA Polymerase II, but Contain an Inactive Form, Phosphorylated on Serine2Residues of the C-Terminal Domain. Molecular Biology of the Cell, 17(4), 1723–1733.

Authors 5
  1. Sheila Q. Xie (first)
  2. Sonya Martin (additional)
  3. Pascale V. Guillot (additional)
  4. David L. Bentley (additional)
  5. Ana Pombo (additional)
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Dates
Type When
Created 19 years, 6 months ago (Feb. 8, 2006, 8:27 p.m.)
Deposited 4 years, 1 month ago (July 23, 2021, 3:10 p.m.)
Indexed 26 minutes ago (Sept. 4, 2025, 6:29 a.m.)
Issued 19 years, 5 months ago (April 1, 2006)
Published 19 years, 5 months ago (April 1, 2006)
Published Print 19 years, 5 months ago (April 1, 2006)
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@article{Xie_2006, title={Splicing Speckles Are Not Reservoirs of RNA Polymerase II, but Contain an Inactive Form, Phosphorylated on Serine2Residues of the C-Terminal Domain}, volume={17}, ISSN={1939-4586}, url={http://dx.doi.org/10.1091/mbc.e05-08-0726}, DOI={10.1091/mbc.e05-08-0726}, number={4}, journal={Molecular Biology of the Cell}, publisher={American Society for Cell Biology (ASCB)}, author={Xie, Sheila Q. and Martin, Sonya and Guillot, Pascale V. and Bentley, David L. and Pombo, Ana}, year={2006}, month=apr, pages={1723–1733} }