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Tyrosine phosphorylations specific to mitosis in human and hamster cells
R Schlegel1, M O Harris, G S Belinsky
1Department of Molecular and Cellular Toxicology Harvard School of Public Health, Boston, Massachusetts 02115, USA.
Abstract:
Changes in protein tyrosine phosphorylation are known to be important for regulating cell cycle progression. With the aim of identifying new proteins involved in the regulation of mitosis, we used an antibody against phosphotyrosine to analyze proteins from synchronized human and hamster cells. At least seven proteins were found that displayed mitosis-specific tyrosine phosphorylation in HeLa cells (pp165, 205, 240, 250, 270, 290, and approximately 400) and one such protein in hamster BHK cells (pp155). In synchronized HeLa and BHK cells, all proteins except HeLa pp165, pp205, and pp250 were readily detectable only in mitosis. Tyrosine phosphorylation of pp165, pp205, and pp250 was apparent during arrest in S phase, suggesting that cell cycle perturbations can affect the phosphorylation state of some of these proteins. In a related finding in BHK cells, pp155 underwent tyrosine phosphorylation when cells were forced into premature mitosis by caffeine treatment. Only one protein (pp135 in HeLa cells) was found to be dephosphorylated on tyrosine during mitosis. The above findings may prove helpful for isolating new cell cycle proteins that are important for both the normal regulation of mitosis and the mitotic aberrations associated with cell cycle perturbations and chemical treatments.
Insights
Researchers identified novel proteins crucial for cell cycle regulation by examining protein tyrosine phosphorylation during mitosis. These findings aid in understanding normal mitosis and aberrations in cell cycle progression.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Protein tyrosine phosphorylation plays a critical role in cell cycle progression.
- Identifying novel proteins involved in mitosis is essential for understanding cell division.
Purpose of the Study:
- To identify new proteins involved in the regulation of mitosis.
- To analyze changes in protein tyrosine phosphorylation during the cell cycle.
Main Methods:
- Used a phosphotyrosine antibody to analyze proteins from synchronized human (HeLa) and hamster (BHK) cells.
- Investigated mitosis-specific tyrosine phosphorylation patterns.
Main Results:
- Identified seven proteins with mitosis-specific tyrosine phosphorylation in HeLa cells (pp165, 205, 240, 250, 270, 290, ~400) and one in BHK cells (pp155).
- Observed tyrosine phosphorylation of some proteins during S phase arrest and premature mitosis induction.
- Found one protein (pp135 in HeLa cells) dephosphorylated on tyrosine during mitosis.
Conclusions:
- Discovered novel cell cycle proteins regulated by tyrosine phosphorylation.
- These findings contribute to understanding normal mitosis and mitotic aberrations.
- Provides a basis for isolating new cell cycle regulatory proteins.