Arsenate-mediated G2 cell cycle arrest in U-2OS cells involves phosphorylation of human polycomb protein 2 by p38...

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• G2/M checkpoints are vital for accurate cell mitosis.
• p38 MAPK activation is known to be essential for stress-induced G2 arrest in U-2OS cells.
• The precise molecular mechanism linking p38 MAPK to G2 arrest remained unclear.

Purpose of the Study:

• To elucidate the molecular mechanism by which p38 MAPK regulates stress-induced G2 arrest.
• To identify direct interactions between p38 MAPK and proteins involved in cell cycle regulation.
• To understand the role of HPC2 phosphorylation in arsenate-induced cell cycle arrest.

Main Methods:

• T7 phage display system to identify protein interactions.
• Cellular assays to assess G2 arrest in U-2OS cells.
• Western blotting and immunoprecipitation to confirm protein binding and phosphorylation.
• Analysis of polycomb repressive complex (PRC) formation and CDC2 expression.

Main Results:

• p38 MAPK was found to directly bind human polycomb protein 2 (HPC2).
• Arsenate-induced G2 arrest in U-2OS cells depends on p38 MAPK and HPC2 phosphorylation.
• Phosphorylation of HPC2 at threonine 495 is necessary for recruiting Ring1 and Rb family proteins to form PRC.
• PRC formation is required for the downregulation of CDC2 expression induced by arsenate.

Conclusions:

• p38 MAPK regulates cell cycle progression by phosphorylating HPC2.
• This phosphorylation event mediates transcriptional repression, linking p38 MAPK to the regulation of gene expression.
• A mechanistic link is established for arsenate-induced transcriptional silencing via the p38 MAPK-HPC2 pathway.