| The human fetal liver(HFL) during 16-24 weeks of gestation is an organ in developmental stage, which has functions in metabolism of carbohydrates fats proteins and so on. Moreover, it is a major site of hematopoiesis in fetus. It will understand the mechanism in fetal liver by discovering the information of proteins in large scale through proteome research. In the proteome research, the low abundance protein is a bottle-neck. At present, there are two main solutions to deal with this problem: to deplete the high abundant proteins and protein fractionation. Based on the characteristics of eukaryotic cell structure, it is possible to fractionate proteins by organelles extraction. In our research, we established the technical platform of nuclei extraction through sucrose density gradient centrifugation. The purity was analyzed by western-blot, enzyme assay and electron microscopy, indicating that the nuclei were enriched more than 5 times. After the nuclei lysed, the nuclear proteins were further fractionated to hydrophobic, hydrophilic and pellet parts by kit. Further, the proteins were separated and identified by one dimensional electrophoresis and mass spectrograph. 422 proteins were identified in which 145 proteins were previously located in nucleus ,16 novel proteins(10 predicted to localized in nucleus) and 9 low abundant proteins in liver according to SWISS-PROT annotation. Moreover, the analysis of characterization and localization of identified proteins showed that the nuclear proteins were basic and hydrophilic. The identified nuclear proteins were structural and RNA splicing proteins, which were expressed ubiquitously among various cells. The tissue-specific classification of proteins demonstrated that many proteins were not only expressed in liver but also highly in testis and brain, suggesting that the proteins might play key biological role.
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