A comparison of transcriptional activation by ER alpha and ER beta

We have compared the ability of ER alpha and ER beta to stimulate transcrip tion from a number of reporter genes in different cell lines and demonstrat e that the activity of AF1 in ER beta is negligible compared with that of E R alpha on ERE based reporters. The activity of AF2 in ER alpha and ER beta is similar and this is likely to reflect their similar ability to bind coa ctivators. As a consequence, when transcription from a gene depends on both AF1 and AF2 the activity of ER alpha greatly exceeds that of ER beta but w hen AF1 is not required ER alpha and ER beta have similar transcriptional a ctivities. (C) 1999 Elsevier Science Ltd. All rights reserved.