SpOct, a gene encoding the major octamer-binding protein in sea urchin embryos: expression profile, evolutionary relationships, and DNA binding of expressed protein.
We have characterized a sea urchin gene, SpOct, that encodes a 78-kDa POU-domain protein related to mammalian Oct-1 and Oct-2. The SpOct protein binds octamer elements in the promoters of the alpha H2B (Bell et al., 1992, Dev. Biol. 150, 363-371) and CyIIIa actin genes, and it closely resembles the major octamer-binding activity obtained from sea urchin blastula nuclear lysates in the size of its DNase I footprint on a canonical octamer element and in its relative binding affinity (Kr) for the octamer element versus poly(dAT) (1.4 x 10(4)). Moreover, partial protein sequences obtained from affinity-purified octamer-binding protein match sequences present in SpOct. These data suggest that SpOct is closely related to, if not identical with, the major octamer-binding activity in blastula nuclear extracts. RNA gel blots reveal four forms of SpOct mRNA, ranging in size from 4 to 12 kb. They are regulated coordinately in the embryo: all are present in the unfertilized egg, increase 28-fold in amount by the 8-hr blastula stage, and decline 6-fold by the 12-hr blastula stage. The same four size classes of SpOct mRNAs are present in several adult tissues, although their relative amounts vary. The temporal profile of SpOct mRNA expression in embryos closely resembles that of the alpha histone H2B gene. Our previous work (Bell et al., 1992) showed that expression of the alpha H2B gene in blastula-stage embryos was entirely dependent on an octamer element. Together, these data strongly suggest that SpOct may be the key regulator of the alpha H2B gene.
Char
B R
BR
Department of Biochemistry and Kenneth R. Norris Cancer Hospital and Research Institute, University of Southern California School of Medicine, Los Angeles 90033.
Bell
J R
JR
Dovala
J
J
Coffman
J A
JA
Harrington
M G
MG
Becerra
J C
JC
Davidson
E H
EH
Calzone
F J
FJ
Maxson
R
R
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D008969:Molecular Sequence Data; D050810:Octamer Transcription Factors; D012617:Sea Urchins / Q000196:embryology / Q000235:genetics*; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D004268:DNA-Binding Proteins; C082470:Oct protein, Strongylocentrotus purpuratus; D050810:Octamer Transcription Factors; D014157:Transcription Factors; D004247:DNA