Figure 2

HSP90α is a prolactin regulated target gene. (a) Dose response of the heat shock protein 90 alpha (HSP90A) gene to prolactin in SKBR3 cells assessed by northern analysis. SKBR3 cells were seeded to achieve low and higher confluence before treatment for one hour with the indicated doses of prolactin (PRL). Total RNA was transferred to a nylon membrane, and the blot probed with the HSP90A gene fragment. (b) Western blot analysis: HSP90α protein is increased about two-fold in SKBR3 cells in response to 5 ug/mL prolactin. (c) Northern analysis: HSP90α mRNA is increased about four-fold in HC11 cells in response to a one hour treatment of lactogenic hormones, prolactin, dexamethasone and insulin (DIP) compared with undifferentiated (U) HC11 cells treated with epidermal growth factor and insulin. (d) Western blot of HSP90α protein extracts from undifferentiated, competent (C) HC11 cells or after DIP treatment for the time indicated. Production of beta-casein is observed after 96 hours when the cells are fully differentiated. Longer exposures show a small amount of beta-casein after 72 hours.