Requirement of a region of STAT5 for Py origin-dependent replication.

(A) Mutants with deletion or Y-residue point mutation are shown schematically. The mutant STAT5 was transfected with 4XSTOICAT (B) or 4XST-Luc (C) into BA/F-wild cells, and the cells were depleted of mIL-3 for 5 hours. hGM-CSF (10 ng/mL) was added and culture was continued for another 24 hours. Cells were harvested, and DpnI (B) or luciferase (C) assay was done as described in “Materials and methods.” Arrow in (B) indicates the replicated plasmid.