hMSH2 expression is driven by AP1-dependent regulation through phorbol-ester exposure

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Mammalian mismatch repair (MMR) is vital for genomic stability and cellular response to DNA damage.
• Understanding the regulation of key MMR proteins like human MutS homolog 2 (hMSH2) is crucial for comprehending MMR dysfunction and its cellular consequences.
• Previous studies indicated protein kinase C (PKC) activity regulates hMSH2 expression in myeloid leukemic cells.

Purpose of the Study:

• To elucidate the regulatory mechanisms controlling hMSH2 expression.
• To investigate the role of protein kinase C (PKC) in modulating hMSH2 levels.
• To identify transcription factors involved in the PKC-mediated regulation of hMSH2.

Main Methods:

• Treatment of U937 cells with phorbol ester (TPA) to activate PKC.
• Analysis of hMSH2 protein and mRNA levels.
• Investigation of hMSH2 promoter activity using site-directed mutagenesis of AP-1 binding sites.
• Utilizing a dominant-negative c-Jun factor to assess AP-1's role in vivo and in vitro.

Main Results:

• PKC activation by TPA leads to increased hMSH2 protein levels, paralleled by elevated hMSH2 mRNA.
• Results suggest transcriptional regulation of the hMSH2 gene upon TPA induction.
• The AP-1 transcription factor is implicated in the transactivation of hMSH2.
• Disruption of AP-1 binding sites or inhibition of c-Jun abolished TPA-induced hMSH2 overexpression.

Conclusions:

• PKC-mediated control of hMSH2 expression is, at least partially, dependent on AP-1 transactivation.
• The findings highlight AP-1 as a key mediator in the transcriptional upregulation of hMSH2 by PKC.
• This regulatory pathway is important for maintaining genomic stability through the MMR system.