title: Phosphorylation of Xenopus transcription factor IIIA by an oocyte protein kinase CK2.
abstract: Transcription factor IIIA (TFIIIA), isolated from the cytoplasmic 7 S ribonucleoprotein complex of Xenopus oocytes, is phosphorylated when incubated with [gamma-(32)P]ATP. This modification is due to a trace kinase activity that remains associated with the factor through several steps of purification. The kinase can use either ATP or GTP, and will phosphorylate casein and phosvitin to the exclusion of TFIIIA. The kinase is reactive with a ten-amino-acid peptide that is a specific substrate for protein kinase CK2 (CK2; formerly casein kinase II). In addition, inhibition of phosphorylation by heparin and stimulation by spermidine indicate that the activity can be ascribed to CK2. Phospho amino acid analysis established that serine is the sole phosphoryl acceptor in TFIIIA. There are four consensus sites for CK2 in TFIIIA; all contain serine residues at the putative site of phosphorylation. TFIIIA immunoprecipitated from oocytes, which were incubated with [(32)P]orthophosphate, is also phosphorylated exclusively on serine residues. Only the cyanogen bromide fragment, which was derived from the N-terminal end of TFIIIA, is labelled in vivo. A recognition sequence for CK2, located at Ser(16) in the beta-turn of the first zinc-finger domain, is the only protein kinase consensus sequence present in this peptide. Assays in vitro with site-specific mutants of TFIIIA established that Ser(16) is the preferred site of phosphorylation, with some secondary modification at Ser(314).
authors.affiliation: Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, Indiana 46556, USA.
authors.forename: Cara J
authors.initials: CJ
authors.lastname: Westmark
authors.forename: Romi
authors.initials: R
authors.lastname: Ghose
authors.forename: Paul W
authors.initials: PW
authors.lastname: Huber
mesh_terms: D019943:Amino Acid Substitution; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D047390:Casein Kinase II; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli; D005260:Female; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000201:enzymology*; D010053:Ovary / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012341:RNA, Ribosomal, 5S / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D000596:Amino Acids; D004268:DNA-Binding Proteins; D010446:Peptide Fragments; D012341:RNA, Ribosomal, 5S; D011994:Recombinant Proteins; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases