A novel human estrogen receptor β:: Identification and functional analysis of additional N-terminal amino acids

A novel human estrogen receptor beta (hER beta) was cloned from human testis mRNA, ovary and thymus cDNA utilizing PCR and 5' RACE methods. The 5' end of hER beta contained an additional open reading frame, in-frame and upstream of the published clones. hER beta encodes a protein of 530 amino acids with an approximate molecular weight of 63 kDa and is larger than the previously reported rat, mouse and human protein. To determine the functional role of additional N-terminal amino acids, we compared the transcription functions of receptor lacking (hER beta(T)) and receptor containing (hER beta(L)) this N-terminal extension. hER beta(L) is more active than hER beta(T) in transactivating ERE-based reporter genes. hER beta(L), but not hER beta(T), attenuated cytokine mediated NF kappa B activation. Taken together, the additional N-terminal amino acids appear to play a role in modulating estrogen responsive gene expression in vitro. (C) 1998 Elsevier Science Ltd. All rights reserved.