Two distinct cellular phosphoproteins bind to the c-fos serum response element

Area of Science:

• Molecular Biology
• Gene Regulation
• Transcription Factors

Background:

• Serum growth factors induce c-fos transcription via a specific DNA sequence, the serum response element (SRE).
• The SRE is known as a binding site for the nuclear protein serum response factor (SRF).
• Direct evidence linking SRF activity to SRE function is lacking.

Purpose of the Study:

• To investigate the binding proteins of the serum response element (SRE).
• To determine if other proteins besides serum response factor (SRF) bind to the SRE.
• To explore the potential for distinct proteins mediating SRE functions.

Main Methods:

• Characterization of SRE-binding proteins using size and chromatographic properties.
• Assessment of binding specificity and nucleotide contact points within the SRE.
• Analysis of cellular extracts for the presence of distinct SRE-binding proteins.

Main Results:

• A second, distinct SRE-binding protein was identified in cells.
• This novel protein differs from SRF in size, chromatographic behavior, and binding specificity.
• The new protein makes unique contacts with nucleotides within the SRE sequence.

Conclusions:

• Cells possess at least two distinct proteins capable of binding to the SRE.
• These distinct SRE-binding proteins may independently mediate the SRE's diverse functions.
• This finding provides a molecular basis for the complex roles of the SRE in gene expression.