FIG. 3.

ERK1 phosphorylates LANA and can prime for GSK-3 phosphorylation in vitro. (A) In vitro ERK1 kinase assay. The autoradiograph examines the incorporation of [γ-³²P]ATP into control GST (lane 1), GST-LANA(C+N) (lane 2), GST-LANA-C (lane 3), GST-LANA-N (lane 4), and synthetic peptide LANA(246-258) (lane 5). (B) In vitro ERK1 priming and GSK-3 kinase assays. The autoradiograph examines the incorporation of [γ-³²P]ATP in a GSK-3 kinase assay performed without priming (top), a control ERK1 priming kinase assay to detect ERK background activity (middle), and an assay in which ERK1 primes for GSK-3 phosphorylation (bottom). Lane 1, control GST; lane 2, GST-LANA-N.