| Summary: | 博士 === 國立臺灣大學 === 分子醫學研究所 === 91 === Part I: Higher Order Arrangement of Nuclear Bodies
Abstract
The nuclei of eukaryotic cells consist of discrete substructures. These substructures include the nuclear bodies, which have been implicated in a number of biological processes such as transcription and splicing. However, for most nuclear bodies, the details of involvement in these processes in relation to their three dimensional distributions in the nucleus are still unclear. Through the analysis of TDP, a protein functional in both transcriptional repression and alternative splicing, we have identified a new category of nuclear bodies within which the TDP molecules reside. Remarkably, the TDP bodies (TB) co-localize or overlap with several different types of nuclear bodies previously suggested to function in transcription or splicing. Of these nuclear bodies, the GEM appears to associate with TB through the interaction between SMN and TDP. Furthermore, TB sometimes appears to be the bridge of two or more of these other nuclear bodies. Our data suggest the existence of a hierarchy, and possibly functional arrangement of the nuclear bodies within the eukaryotic nuclei.
Part II: Reorganization of Nuclear Bodies during Stress Induced by Transcription Inhibition
Abstract
Changes in levels of transcription, pre-m RNA splicing and RNP assembly are depended on spatial aspects of organization, including chromatin structure and regulation of nuclear bodies. Nuclear bodies are dynamic structures, responding to the cellular environment. Reorganization of the structure of nuclear bodies has been suggested during statues of transcriptional inhibition. However, it is not clear. Most of studies focus on dynamic regulation of splicing factors and RNAP II, because these molecules involved in the transcription machinery. Therefore, we are interested to analyze the regulation of nuclear bodies in more detail. We examined spatial distribution, structure and the mechanism of well known nuclear bodies including nucleous, ICGCs (SC35 speckles), Cajal bodies (CBs), Gem (SMN protein complex), and PODs (PML bodies) as demonstrated by 3-D image analysis in cell induced by RNA polymerase II inhibitor. Striking structure changes of nucleous, SC35 speckles and CBs are observed. The SC35 speckles and Cajal bodies appear a cylinder after treatment with transcription inhibitor, includingα- amanitin, DRB and actinomycine D. Interestingly, we find RNAPIILS located inside the cylinder of SC35 speckles. Again, two types of cylinder of CBs can be observed, one is surrounded nucleolus and another is outside nucleolus and fibrillarin colocalized with coilin or localized inside the cylinder of CBs. The result is similar to the early development characterized by a period where both pol I and pol II —dependent transcription remain switched off. Cytochalasin B, actin polymerlization inhibitor, inhibits formation of cylinder and decrease survive rate. Our results suggest that striking reorganization of nuclear bodies occurred in somatic cell during transcriptional inhibition and provide the emerging role for polymerization of nuclear actin.
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