Basic fibroblast growth factor activates serum response factor gene expression by multiple distinct signaling...

Area of Science:

• Molecular Biology
• Cell Signaling
• Gene Regulation

Background:

• Serum response factor (SRF) is crucial for mammalian cell responses to extracellular signals.
• SRF regulates early response genes involved in cell growth and differentiation.
• Regulation of the SRF gene itself is less understood than its transcriptional activation mechanism.

Purpose of the Study:

• To elucidate the regulatory mechanisms of the SRF gene promoter in response to basic fibroblast growth factor (bFGF).
• To identify distinct pathways involved in SRF promoter upregulation by bFGF.
• To explore the role of specific regulatory elements like CArG boxes and ETS binding sites.

Main Methods:

• Analysis of SRF promoter activity in response to bFGF stimulation.
• Identification of key regulatory elements (ETS, Sp/Egr-1, CArG boxes) involved in SRF gene upregulation.
• Investigation of signaling pathways (Rho, Ras) mediating promoter activation.

Main Results:

• bFGF upregulates the SRF promoter through at least two independent mechanisms.
• A CArG box-independent mechanism involves an ETS binding site.
• A novel CArG box-dependent mechanism requires both Sp factor and CArG motifs for maximal stimulation.
• The CArG box-dependent component is targeted by Rho, while the Sp site-dependent component is targeted by Ras.

Conclusions:

• SRF promoter regulation by bFGF is complex, involving distinct CArG-dependent and independent pathways.
• Rho and Ras signaling pathways differentially regulate SRF gene expression.
• Findings have implications for understanding SRF and bFGF roles in cardiogenesis during development.