GA-binding protein regulates KIS gene expression, cell migration, and cell cycle progression

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The cyclin-dependent kinase inhibitor p27(Kip1) regulates cell cycle progression.
• The serine/threonine kinase KIS phosphorylates p27(Kip1), leading to its degradation.
• The transcriptional regulation and biological activity of the KIS gene are unknown.

Purpose of the Study:

• To elucidate the molecular mechanisms of human KIS gene transcriptional activation.
• To investigate the biological role of KIS gene expression in cell migration and cell cycle progression.

Main Methods:

• Promoter activity assays using deletion constructs and site-directed mutagenesis.
• Identification of transcription factor binding sites using electrophoretic mobility shift assays.
• siRNA-mediated knockdown of GA-binding protein alpha (GABPalpha) in vascular smooth muscle cells and mouse embryonic fibroblasts.
• In vivo studies using a mouse model of vascular injury.

Main Results:

• The transcription initiation site of the KIS gene was mapped 116 bp upstream of the translation start site.
• Sequences between -141 and the transcription start site were sufficient for maximal promoter activity.
• Two Ets-binding sites within this region were crucial for promoter activity, binding GA-binding protein (GABP).
• Knockdown of GABPalpha reduced KIS gene expression, cell migration, and increased p27(Kip1) levels.
• GABPalpha-deficient cells showed reduced cell cycle progression.
• GABPalpha-heterozygous mice exhibited reduced KIS expression and smaller arterial lesions after vascular injury.

Conclusions:

• Serum-responsive GABP binding to Ets-binding sites activates the KIS promoter.
• KIS gene expression, regulated by GABP, plays a role in cell migration and cell cycle progression.
• These findings identify a novel regulatory pathway involving GABP and KIS in vascular smooth muscle cell dynamics.