Repression of p53 activity by Smyd2-mediated methylation

Area of Science:

• Biochemistry
• Molecular Biology
• Epigenetics

Background:

• Lysine methylation is a key epigenetic modification regulating gene transcription.
• The tumor suppressor protein p53 (protein 53) is a non-histone protein regulated by lysine methylation.
• Specific methylation sites on histones and non-histone proteins can lead to transcriptional activation or repression.

Purpose of the Study:

• To identify and characterize novel lysine methylation sites on p53.
• To investigate the role of the lysine methyltransferase Smyd2 in p53 regulation.
• To elucidate the functional consequences of p53 methylation on transcriptional activity and tumor suppression.

Main Methods:

• Mass spectrometry to identify p53 methylation sites.
• Site-directed mutagenesis to analyze methylation-deficient p53 mutants.
• Short interfering RNA (siRNA) to deplete Smyd2 levels.
• Western blotting and chromatin immunoprecipitation assays to assess protein levels and promoter association.
• Reporter assays to measure p53-mediated transcriptional activity.

Main Results:

• Smyd2 methylates p53 at a novel site, Lys 370.
• Lys 370 methylation represses p53-mediated transcriptional activity.
• Smyd2 depletion enhances p53-mediated apoptosis.
• Methylation of Lys 372 by Set9 inhibits Smyd2-mediated methylation of Lys 370.
• Lys 372 methylation blocks the interaction between p53 and Smyd2.

Conclusions:

• p53 is subject to both activating and repressing lysine methylation, similar to histones.
• Smyd2-mediated methylation of Lys 370 represses p53's tumor suppressive function.
• Cross-talk between Set9 and Smyd2 methylation sites provides complex regulatory control over p53.
• Smyd2 may act as an oncogene by inhibiting p53's tumor suppressive activity.