Mitotic Kinases Aurora-A, Plk1, and Cdk1 Interact with Elk-1 Transcription Factor through the N-Terminal Domain

Figure 4

In vitro kinase assay for phosphorylation of various Elk-1 peptides by AurA, AurB, Plk1, and Cdk1 kinases. Unmodified peptides (for sequences see Suppl Table 4) were incubated with indicated kinases in the presence or absence of ATP, and phosphorylation was monitored by accumulation of ADP at 15, 30, 45, and 60 min time points. Reaction tube containing only reaction buffer was used as mock, and kinase activity was reported as relative fluorescence units: (a) phosphorylation of Ser106 peptide witth Plk1, (b) phosphorylation of Thr108 peptide with Plk1, (c) phosphorylation of Thr133 peptide with Cdk1, (d) phosphorylation of Ser198 peptide with AurA, (e) phosphorylation of Ser198 peptide with AurB, (f) phosphorylation of Thr199 peptide with AurA, (g) phosphorylation of Thr199 peptide with AurB, (h) phosphorylation of Ser200 peptide with AurA, (i) phosphorylation of Ser200 peptide with AurB, (j) phosphorylation of Ser202 peptide with Cdk1, (k) phosphorylation of Ser303 peptide with Cdk1, (l) phosphorylation of Ser304 peptide with Cdk1, (m) phosphorylation of Ser324 peptide with Cdk1, and (n) phosphorylation of Ser326 peptide with Cdk1. Reaction tube containing only reaction buffer was used as mock.