Fig. 1.

SF1 Is Phosphorylated by CDKs

A, Endogenous SF1 was isolated from H295R nuclear extract (10 mg) by DPD using a biotinylated double-stranded oligonucleotide containing SFREs and streptavidin-conjugated agarose beads. Eluates (DPD) were run on 10% SDS-PAGE and stained with Coomassie blue (left panel) or subjected to Western blotting with an SF1 antibody (right panel). The proteins present in the bands (in the left panel were identified by mass spectrometry (please see main text for details). MW, Molecular weight standard. B, H295R cells were treated with okadaic acid (100 nm) for 1 h, and SF1 was isolated by DPD. Eluates were subjected to Western blotting with the anti-phospho-(Ser and/or Thr) kinase substrate antibodies for CDKs, PKA, Akt, and PKC. WB, Western blot.