Repression of p53-dependent sequence-specific transactivation by MEF2c

Area of Science:

• Molecular Biology
• Genetics
• Cancer Research

Background:

• The p53 tumor suppressor protein plays a critical role in cellular responses to DNA damage.
• Identifying novel proteins that interact with or regulate p53 function is crucial for understanding cancer development.
• The spleen is a known site of immune activity, but the expression of certain transcription factors like MEF2c has not been extensively studied there.

Purpose of the Study:

• To identify novel proteins interacting with p53-binding DNA sequences.
• To investigate the function of isolated clones, particularly their effect on p53-deficient cells.
• To determine if MEF2c has a role in regulating p53 activity.

Main Methods:

• Construction of a Lambda ZAP cDNA library from p53-deficient mouse spleen.
• Screening the library using a South-Western technique with a p53-specific DNA binding fragment (Fragment A).
• Characterization of isolated clones, including sequence analysis and functional assays on osteosarcoma cell lines.

Main Results:

• Six clones were isolated, with one identified as MEF2c, a MADS-family transcription factor.
• MEF2c gene transcripts were detected in the spleen, an expression site not previously reported.
• Other isolated clones exhibited growth-suppression activity on p53-deficient Saos II cells.
• MEF2c repressed the transactivation of Fragment A by p53 in functional assays.

Conclusions:

• MEF2c is expressed in the spleen.
• MEF2c may function as a negative regulator of p53-responsive elements.
• This finding suggests a novel mechanism of p53 regulation involving MEF2c.