Document Detail

The distribution of RNA polymerase II largest subunit (RPB1) in the Xenopus germinal vesicle.
MedLine Citation:
PMID:  12490164     Owner:  NLM     Status:  MEDLINE    
We describe the localization of the largest subunit of RNA polymerase II (RPB1) in the oocyte nucleus of Xenopus laevis. A single oocyte nucleus contains 18 lampbrush chromosomes, approximately 1500 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 RPB1 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 15-17 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.
Olivia Doyle; Jeffry L Corden; Christine Murphy; Joseph G Gall
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of structural biology     Volume:  140     ISSN:  1047-8477     ISO Abbreviation:  J. Struct. Biol.     Publication Date:    2002 Oct-Dec
Date Detail:
Created Date:  2002-12-19     Completed Date:  2003-06-27     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  9011206     Medline TA:  J Struct Biol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  154-66     Citation Subset:  IM    
Department of Embryology, Carnegie Institution, 115 West University Parkway, Baltimore, MD 21210, USA.
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MeSH Terms
Blotting, Western
Cell Nucleus / metabolism
Coiled Bodies / metabolism
Drosophila melanogaster
Glutathione Transferase / metabolism
Microscopy, Fluorescence
Ovary / metabolism*
RNA Polymerase II / biosynthesis*
RNA, Messenger / metabolism
Recombinant Fusion Proteins / metabolism
Transcription, Genetic
Xenopus laevis / metabolism*
Grant Support
Reg. No./Substance:
0/RNA, Messenger; 0/Recombinant Fusion Proteins; EC Transferase; EC 2.7.7.-/RNA Polymerase II

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