Figure 1

Prolactin-STAT5-mediated signal transduction in SKBR3 cells. (a) Electrophoretic mobility shift assays were carried out with a radioactively labelled β-casein gene promoter probe and protein extracts of SKBR3 cells treated for one hour with the indicated amounts of prolactin (PRL). The arrows indicate the positions of the signal transducers and activators of transcription (STAT5) DNA complex and of a supershifted complex formed in the presence of a STAT5 specific antibody (Ab). (b) SKBR3 cells were seeded one day, the next day starved of serum overnight and the following day were stimulated (or not) with 5 μg/ml prolactin for the times indicated in the absence of cycloheximide (CHX) unless indicated. In each lane 20 μg of RNA were applied. The northern blot was first hybridised with labelled DNA encoding cytokine inducible SH2 containing protein (CIS) and then rehybridised with a glyceraldehyde 3-phosphate dehydrogenase (GAPDH) specific probe.