The GAGA protein of Drosophila is phosphorylated by CK2.
The GAGA factor of Drosophila is a sequence-specific DNA-binding protein that contributes to multiple processes from the regulation of gene expression to the structural organisation of heterochromatin and chromatin remodelling. GAGA is known to interact with various other proteins (tramtrack, pipsqueak, batman and dSAP18) and protein complexes (PRC1, NURF and FACT). GAGA functions are likely regulated at the level of post-translational modifications. Little is known, however, about its actual pattern of modification. It was proposed that GAGA can be O-glycosylated. Here, we report that GAGA519 isoform is a phosphoprotein that is phosphorylated by CK2 at the region of the DNA-binding domain. Our results indicate that phosphorylation occurs at S388 and, to a lesser extent, at S378. These two residues are located in a region of the DNA-binding domain that makes no direct contact with DNA, being dispensable for sequence-specific recognition. Phosphorylation at these sites does not abolish DNA binding but reduces the affinity of the interaction. These results are discussed in the context of the various functions and interactions that GAGA supports.
Bonet
Carles
C
Departament de Biologia Molecular i Cel.lular, Institut de Biologia Molecular de Barcelona, IBMB-CSIC, Parc Científic de Barcelona, Josep Samitier, 1-5. 08028 Barcelona, Spain.
Fernández
Irene
I
Aran
Xavier
X
Bernués
Jordi
J
Giralt
Ernest
E
Azorín
Fernando
F
D000818:Animals; D047390:Casein Kinase II / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D024202:Electrophoretic Mobility Shift Assay; D006868:Hydrolysis; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D014157:Transcription Factors; C063460:Trl protein, Drosophila; D004247:DNA; D047390:Casein Kinase II