Subnuclear Localization and Dynamics of the Pre-mRNA 3′ End Processing Factor Mammalian Cleavage Factor I 68-kDa Subunit
- 1 April 2007
- journal article
- Published by American Society for Cell Biology (ASCB) in Molecular Biology of the Cell
- Vol. 18 (4), 1282-1292
- https://doi.org/10.1091/mbc.e06-09-0846
Abstract
Mammalian cleavage factor I (CF Im) is an essential factor that is required for the first step in pre-mRNA 3′ end processing. Here, we characterize CF Im68 subnuclear distribution and mobility. Fluorescence microscopy reveals that in addition to paraspeckles CF Im68 accumulates in structures that partially overlap with nuclear speckles. Analysis of synchronized cells shows that CF Im68 distribution in speckles and paraspeckles varies during the cell cycle. At an ultrastructural level, CF Im68 is associated with perichromatin fibrils, the sites of active transcription, and concentrates in interchromatin granules-associated zones. We show that CFIm68 colocalizes with bromouridine, RNA polymerase II, and the splicing factor SC35. On inhibition of transcription, endogenous CF Im68 no longer associates with perichromatin fibrils, but it can still be detected in interchromatin granules-associated zones. These observations support the idea that not only splicing but also 3′ end processing occurs cotranscriptionally. Finally, fluorescence recovery after photobleaching analysis reveals that the CF Im68 fraction associated with paraspeckles moves at a rate similar to the more dispersed molecules in the nucleoplasm, demonstrating the dynamic nature of this compartment. These findings suggest that paraspeckles are a functional compartment involved in RNA metabolism in the cell nucleus.Keywords
This publication has 42 references indexed in Scilit:
- Regulating Gene Expression through RNA Nuclear RetentionCell, 2005
- Dynamic Sorting of Nuclear Components into Distinct Nucleolar Caps during Transcriptional InhibitionMolecular Biology of the Cell, 2005
- Proteomic Analysis of Interchromatin Granule ClustersMolecular Biology of the Cell, 2004
- Nuclear speckles: a model for nuclear organellesNature Reviews Molecular Cell Biology, 2003
- Cajal Bodies: The First 100 YearsAnnual Review of Cell and Developmental Biology, 2000
- Perichromatin fibrils are in situ forms of nascent transcriptsTrends in Cell Biology, 1994
- Immunocytochemistry of the cell nucleusElectron Microscopy Reviews, 1990
- Identification of a nuclear protein component of interchromatin granules using a monoclonal antibody and immunogold electron microscopyExperimental Cell Research, 1984
- Fine structural organization of the interphase nucleus in some mammalian cellsJournal of Ultrastructure Research, 1969
- A new staining procedure for electron microscopical cytologyJournal of Ultrastructure Research, 1969