Isolation of the B3 transcription factor of the Xenopus TFIIIA gene.
The selective expression of the Xenopus TFIIIA gene in immature oocytes is principally regulated by a single 5'-flanking DNA sequence element, termed element 3 (i.e. E3). We describe the isolation and characterization of a cDNA for a protein present in immature Xenopus ooctyes, termed B3.65, which appears to bind to and activate E3-mediated expression. The approximate molecular weight of the E3 binding protein(s) was determined by ultraviolet light cross-linking analysis. B3.65, a protein of the appropriate molecular weight, was purified biochemically from immature Xenopus ooctye extracts by affinity chromatography. Antiserum to purified B3.65 super-shifted the E3 activator complex. In addition, B3.65 mRNA was found to be highly enriched in immature oocytes. All of these data are consistent with B3.65 either being the E3 activator, or antigenically related to the specific activator required for XenopusTFIIIA gene transcription. B3.65 is a member of the K-homologous (KH) domain family of proteins, with almost absolute identity to Xenopus Vg1 RBP/VERA (97%) and significant similarity to human koc (82%). The koc mRNA is over-expressed in human pancreatic cancer tissues, and B3.65 mRNA was detected in Xenopus pancreas and kidney. Interestingly, KH proteins, like Vg1RBP/VERA, are most commonly associated with RNA metabolism, in their capacity to regulate RNA localization, stability, and translation. Our results suggest that B3.65 is a key regulator of both RNA- and DNA metabolism.
Griffin
David
D
Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
Penberthy
W Todd
WT
Lum
Helen
H
Stein
Roland W
RW
Taylor
William L
WL
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D015152:Blotting, Northern; D004268:DNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000378:metabolism; D047108:Embryonic Development; D005260:Female; D018507:Gene Expression Regulation, Developmental; D046911:Macromolecular Substances; D008297:Male; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009865:Oocytes / Q000378:metabolism; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D035582:Transcription Factor TFIIIA / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D014158:Transcription, Genetic; D029867:Xenopus Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics* / Q000378:metabolism
C478062:B3.65 protein, Xenopus; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D012333:RNA, Messenger; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors; D029867:Xenopus Proteins