IDENTIFICATION OF ESTROGEN-RESPONSIVE GENES IN NEUROBLASTOMA SK-ER3 CELLS

To evaluate the role of estrogen receptor in the differentiation of ce lls of neural origin, we developed a molecular approach aimed at the i dentification of estrogen target genes by mRNA differential display PC R (ddPCR) in human neuroblastoma SK-ER3 cells. More than 3000 RNAs wer e examined, a few of which displayed a differential regulation pattern in response to 17 beta-estradiol (E-2). Sequence analysis of three di fferentially amplified ddPCR products showed homology with the growth- associated nuclear protein prothymosin-alpha (PTMA), the Bcl2-interact ing protein Nip2, and one mRNA previously described by others in fetal human brain. Two ddPCR products, referred to as P4 and P10, correspon ded to new DNA sequences. Northern analysis confirmed that estrogen tr eatment of SK-ER3 cells resulted in the upregulation and downregulatio n of expression of these messages. In particular, PTMA was found to ac cumulate at both 1 and 17 hr after E-2 treatment, whereas P10 product accumulated only at 1 hr. Conversely, P4, Nip2, and the fetal brain-re lated mRNAs were significantly decreased by the treatment. Further tim e course analysis of PTMA and Nip2 mRNAs levels indicated that the hor mone exerted a marked biphasic regulatory effect on expression of both messages during the course of cell differentiation. In the present st udy we report for the first time the identification of a panel of estr ogen target genes in neural cells that provide new insights in the mol ecular mechanism of action of E-2 in cells of neural origin.