In vivo kinetics of Cajal body components.
Cajal bodies (CBs) are subnuclear domains implicated in small nuclear ribonucleoprotein (snRNP) biogenesis. In most cell types, CBs coincide with nuclear gems, which contain the survival of motor neurons (SMN) complex, an essential snRNP assembly factor. Here, we analyze the exchange kinetics of multiple components of CBs and gems in living cells using photobleaching microscopy. We demonstrate differences in dissociation kinetics of CB constituents and relate them to their functions. Coilin and SMN complex members exhibit relatively long CB residence times, whereas components of snRNPs, small nucleolar RNPs, and factors shared with the nucleolus have significantly shorter residence times. Comparison of the dissociation kinetics of these shared proteins from either the nucleolus or the CB suggests the existence of compartment-specific retention mechanisms. The dynamic properties of several CB components do not depend on their interaction with coilin because their dissociation kinetics are unaltered in residual nuclear bodies of coilin knockout cells. Photobleaching and fluorescence resonance energy transfer experiments demonstrate that coilin and SMN can interact within CBs, but their interaction is not the major determinant of their residence times. These results suggest that CBs and gems are kinetically independent structures.
Dundr
Miroslav
M
National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA. dundrm@mail.nih.gov
Hebert
Michael D
MD
Karpova
Tatiana S
TS
Stanek
David
D
Xu
Hongzi
H
Shpargel
Karl B
KB
Meier
U Thomas
UT
Neugebauer
Karla M
KM
Matera
A Gregory
AG
Misteli
Tom
T
D000818:Animals; D002466:Cell Nucleolus / Q000737:chemistry / Q000378:metabolism; D020541:Coiled Bodies / Q000737:chemistry / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein; D036681:Fluorescence Recovery After Photobleaching; D031541:Fluorescence Resonance Energy Transfer; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D051379:Mice; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D012326:RNA Splicing; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism; D055532:SMN Complex Proteins; D017381:Spliceosomes / Q000378:metabolism; D013997:Time Factors
D017362:Cyclic AMP Response Element-Binding Protein; D046911:Macromolecular Substances; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D017411:Ribonucleoproteins, Small Nuclear; D055532:SMN Complex Proteins; C068921:p80-coilin