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Published June 1995 | public
Journal Article

SpGCF1, a Sea Urchin Embryo DNA-Binding Protein, Exists as Five Nested Variants Encoded by a Single mRNA


Several Strongylocentrotus purpuratus gene cis-regulatory regions contain asymmetric C_4 sequences which are core elements of target sites for a specific DNA-protein interaction. Blastula stage nuclear extract contains five proteins which specifically bind to these target sites, resulting in a characteristic pattern of complexes in gel mobility shift assays. We used automated affinity chromatography to purify a protein which binds to these sites and have isolated the corresponding cDNA. This protein, SpGCF1, is a novel sea urchin DNA-binding protein with no overall homology to proteins reported in the databases currently available. The DNA-binding domain of this protein was identified by a deletion analysis. As demonstrated both for protein translated in vitro and for bacterial protein expressed from a cDNA clone, a single SpGCF1 mRNA serves as a template for the synthesis of five DNA-binding polypeptides. We show that these five polypeptides are most likely produced by differential usage of a nested set of AUG start codons in the SpGCF1 cDNA and thus contain variable amounts of a proline-rich N-terminal domain. Since proline-rich regions often serve as transcriptional activation domains, the five SpGCF1 proteins apparently possess different "activation potentials."

Additional Information

© 1995 Academic Press, Inc. Accepted March 17, 1995. We are grateful to Professors Carl Parker and Scott Fraser of this Institute for critical reviews of the manuscript. This research was supported by NIH Grant HD-05753. R.W.Z. was an AASERT awardee of the ONR.

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