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 C4 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."
Zeller
R W
RW
Division of Biology, California Institute of Technology, Pasadena 91125, USA.
Coffman
J A
JA
Harrington
M G
MG
Britten
R J
RJ
Davidson
E H
EH
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics*; D012617:Sea Urchins / Q000196:embryology / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; C092981:SpGCF1 protein, Strongylocentrotus purpuratus; D014157:Transcription Factors; D004247:DNA