mRNP3 and mRNP4 are phosphorylatable by casein kinase II in Xenopus oocytes, but phosphorylation does not modify RNA-binding affinity.
mRNP3 and mRNP4 (also called FRGY2) are two mRNA-binding proteins which are major constituents of the maternal RNA storage particles of Xenopus laevis oocytes. The phosphorylation of mRNP3-4 has been implicated in the regulation of mRNA masking. In this study, we have investigated their phosphorylation by casein kinase II and its consequence on their affinity for RNA. Comparison of the phosphopeptide map of mRNP3-4 phosphorylated in vivo with that obtained after phosphorylation in vitro by purified Xenopus laevis casein kinase II strongly suggests that casein kinase II is responsible for the in vivo phosphorylation of mRNP3-4 in oocytes. The phosphorylation occurs on a serine residue in a central domain of the proteins. The affinity of mRNP3-4 for RNA substrates remained unchanged after the treatment with casein kinase II or calf intestine phosphatase in vitro. This suggests that phosphorylation of these proteins does not regulate their interaction with RNA but rather controls their interactions with other proteins.
Deschamps
S
S
Centre de Génetique Moléculaire, Laboratoire du Centre National de la Recherche Scientifique, Université P. et M.Curie (Paris VI), Gif-sur-Yvette, France.
Jacquemin-Sablon
H
H
Triqueneaux
G
G
Mulner-Lorillon
O
O
Potier
M
M
Le Caer
J P
JP
Dautry
F
F
le Maire
M
M
D000595:Amino Acid Sequence; D000818:Animals; D047390:Casein Kinase II; D008969:Molecular Sequence Data; D009865:Oocytes / Q000201:enzymology / Q000378:metabolism* / Q000502:physiology; D010748:Phosphopeptides / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism* / Q000502:physiology; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology; D012694:Serine / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism* / Q000502:physiology; D029867:Xenopus Proteins; D014982:Xenopus laevis
D010748:Phosphopeptides; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; C075593:YBX2 protein, Xenopus; D012694:Serine; D012313:RNA; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases