| Summary: | 碩士 === 臺灣大學 === 生化科學研究所 === 98 === The post-translational modifications of histones are relevant to many important cellular regulation mechanisms essential for cell proliferation and gene expression. In the histones extracted from HeLa cells, incorporation of spermine, presumably by covalent modification, was detected. Interestingly, these polyamines also play a key role in the regulation of cell proliferation.
From our results, we showed that spermine is covalently attached to extracted histones derived from HeLa cells. Comparing the western blotting results of extracted histones with that of recombinant human core histones and other proteins which have similar features to histones, we detected positive anti-spermine signals in histones H3, H2B and H4. This was further confirmed in our TAU/SDS 2D PAGE data.
Since tissue transglutaminase (TG2) is the main enzyme catalyzing the protein-polyamine incorporations, we confirmed that TG2 expressed in the nuclei of HeLa cells, and that histones were the in vitro acyl donor substrates of TG2. However, from the in vitro transamidation assay, we found that only H2B could be modified. Treatment of HeLa cells with cystamine, a TG2 inhibitor, did not alter the spermine-conjugation levels in core histones.
Furthermore, we synchronized the HeLa cells by lovastatin treatments and harvested the cells every four hours after release of lovastatin inhibition to determine the levels of spermine incorporation. We found that cells in the G2/M phase of the cell cycle had higher levels of spermine incorporation compared to those in the other stages. These results may imply a functional role of the modification of histones by spermine in cell cycle regulations.
|
|---|
