Nucleolar Components Involved in Ribosome Biogenesis Cycle between the Nucleolus and Nucleoplasm in Interphase Cells

摘要: We examined the mobilities of nucleolar components that act at various steps ribosome biogenesis pathway. Fluorescence recovery after photobleaching (FRAP) and fluorescence loss in (FLIP) analyses demonstrate factors involved rRNA transcription (upstream-binding factor [UBF]), processing (nucleolin, fibrillarin, RNase MRP subunits, Rpp29), assembly (B23) exchange rapidly between nucleoplasm nucleolus. In contrast, ribosomal subunit proteins (S5, L9) are much slower. Selective inhibition RNA polymerase I does not prevent exchanges but influences rates differentially for different components. These findings suggest rapid nucleolus may represent a new level regulation synthesis. The dynamic properties imply association these is due to their specific functional roles rather than simply nucleolar-targeting events.