title: Casein kinase II phosphorylates Ser468 in the PEST domain of the Drosophila IkappaB homologue cactus.
abstract: Cactus protein is a Drosophila homologue of the mammalian IkappaB family of cytoplasmic anchor proteins. In unstimulated cells they function to retain rel/NFkappaB transcription factors in the cytoplasm but are rapidly degraded in response to signalling. The destruction of cactus or IkappaBalpha allows the rel/NFkappaB transcription factor to relocalise to the nucleus. Cactus is a phosphoprotein and has in its C-terminus a PEST protein stability domain. In this paper we show that, like mammalian IkappaBalpha, the PEST domain of cactus is phosphorylated by casein kinase II. We have localised the site of modification to a single residue, Ser468, and find no evidence for additional phosphorylation sites. The conservation of these sites in mammalian and invertebrate cytoplasmic anchor proteins suggests that phosphorylation by casein kinase II may play a critical functional role, plausibly in the regulation of constitutive or inducible proteolysis.
authors.affiliation: Department of Biochemistry, University of Cambridge, UK.
authors.forename: L C
authors.initials: LC
authors.lastname: Packman
authors.forename: K
authors.initials: K
authors.lastname: Kubota
authors.forename: J
authors.initials: J
authors.lastname: Parker
authors.forename: N J
authors.initials: NJ
authors.lastname: Gay
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D047390:Casein Kinase II; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins; D004563:Electrochemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli; D006160:Guanosine Triphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000378:metabolism*; D051841:Transcription Factor RelB; D014157:Transcription Factors
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D051841:Transcription Factor RelB; C077938:cact protein, Drosophila; C036852:magnesium GTP; D012694:Serine; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases