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| The distribution of RNA polymerase II largest subunit (RPB1) in the Xenopus germinal vesicle |
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| Author(s): Doyle O, Corden JL, Murphy C, Gall JG |
| Source: JOURNAL OF STRUCTURAL BIOLOGY Volume: 140 Issue: 1-3 Pages: 154-166 Published: OCT-DEC 2002 |
| Times Cited: 27 References: 53 |
| Abstract: We describe the localization of the largest subunit of RNA polymerase 11 (RPB1) in the oocyte nucleus of Xenopus laevis. A single oocyte nucleus contains IS lampbrush chromosomes, similar to1500 extrachromosomal nucleoli, 50-100 Cajal bodies (CBs) and hundreds to thousands of B-snurposomes. CBs contain many factors involved in RNA transcription and processing, whereas B-snurposomes contain a subset of these factors involved in mRNA processing. Immunofluorescent staining demonstrates that most RPB1 is in the nucleoplasm and that the heptapeptide repeat comprising its carboxy-terminal domain (CTD) is not phosphorylated. A minor fraction of RPB I is associated with the transcription units of the lampbrush chromosomes and is phosphorylated on serines 2 and 5 of the CTD. Another minor fraction occurs in CBs, which react with antibodies against unphosphorylated CTD repeats and repeats phosphorylated on serine 5. Although B-snurposomes are stained by an antibody against phosphorylated RPB1 (mAb H5), we present evidence that this stain is due to cross-reaction with one or more SR proteins. We show that constructs consisting of 1517 CTD heptapeptide repeats fused to glutathione-S-transferase are targeted rapidly and specifically to CBs but not to B-snurposomes after injection into the nucleus. The staining and targeting data define at least three distinct populations of RPB1 in the GV with different states of phosphorylation. We suggest that CBs play a unique role in RPB1 metabolism, possibly as sites for assembly or modification of transcription complexes. (C) 2002 Elsevier Science (USA). All rights reserved. |
| Document Type: Proceedings Paper |
| Language: English |
| Reprint Address: Gall, JG (reprint author), Carnegie Inst Washington, Dept Embryol, 115 W Univ Pkwy, Baltimore, MD 21210 USA |
Addresses:
1. Carnegie Inst Washington, Dept Embryol, Baltimore, MD 21210 USA
2. Johns Hopkins Univ, Dept Biol, Baltimore, MD 21218 USA
3. Johns Hopkins Univ, Sch Med, Dept Mol Biol & Genet, Baltimore, MD 21205 USA |
| Publisher: ACADEMIC PRESS INC ELSEVIER SCIENCE, 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA |
| Subject Category: Biochemistry & Molecular Biology; Biophysics; Cell Biology |
| IDS Number: 627VW |
| ISSN: 1047-8477 |
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