Sequence and Expression of Human Estrogen Receptor Complementary DNA

TLDR

The mechanism by which estrogen and other steroid hormone receptors regulate gene expression in eukaryotic cells is poorly understood. This study sequenced a full‑length cDNA clone of the estrogen receptor from MCF‑7 breast cancer cells and expressed it in CHO‑K1 cells to produce a functional protein. The cloned cDNA was expressed in CHO‑K1 cells, and the resulting protein bound estradiol and sedimented as a 4S complex in salt‑containing sucrose gradients and as an 8–9S complex without salt. The expressed protein corresponded to a 1785‑nt open reading frame encoding a 595‑amino‑acid polypeptide of 66,200 Da, matched estradiol binding and 4S/8–9S sedimentation, reacted with a primate‑specific ER monoclonal antibody, and its amino‑acid sequence revealed significant homology with the human glucocorticoid receptor and v‑erb A, suggesting a shared ancestral gene and a cysteine‑rich DNA‑binding domain.

Abstract

The mechanism by which the estrogen receptor and other steroid hormone receptors regulate gene expression in eukaryotic cells is not well understood. In this study, a complementary DNA clone containing the entire translated portion of the messenger RNA for the estrogen receptor from MCF-7 human breast cancer cells was sequenced and then expressed in Chinese hamster ovary (CHO-K1) cells to give a functional protein. An open reading frame of 1785 nucleotides in the complementary DNA corresponded to a polypeptide of 595 amino acids and a molecular weight of 66,200, which is in good agreement with published molecular weight values of 65,000 to 70,000 for the estrogen receptor. Homogenates of transformed Chinese hamster ovary cells contained a protein that bound [ 3 H]estradiol and sedimented as a 4S complex in salt-containing sucrose gradients and as an 8 to 9S complex in the absence of salt. Interaction of this receptor-[ 3 H]estradiol complex with a monoclonal antibody that is specific for primate ER confirms the identity of the expressed complementary DNA as human estrogen receptor. Amino acid sequence comparisons revealed significant regional homology among the human estrogen receptor, the human glucocorticoid receptor, and the putative v- erb A oncogene product. This suggests that steroid receptor genes and the avian erythroblastosis viral oncogene are derived from a common primordial gene. The homologous region, which is rich in cysteine, lysine, and arginine, may represent the DNA-binding domain of these proteins.