In our current study, we found that TRIM3, an E3 ligase, can promote ER alpha signaling activity and breast cancer progression. Ubiquitin-based immunoprecipitation assays were used to detect the specific ubiquitination modification on the ER alpha protein. Protein stability assays and ubiquitin assays were used to detect ER alpha protein degradation. Identification of ER alpha signaling activity was accomplished with luciferase assays, RT–PCR and western blotting. RNA sequencing data were analyzed by Ingenuity Pathway Analysis. A CCK-8 assay was used to measure cell viability. TRIM3 and ER alpha protein expression levels were measured by western blotting, while the mRNA levels of ER alpha target genes were measured by RT–PCR. Thus, decoding the throughput of estrogen signaling, including the control of ER alpha expression and stability, is critical for the improvement of breast cancer therapeutics. Approximately half of ER alpha-positive breast cancer patients will eventually develop endocrine resistance, making it a major clinical challenge in therapy. Selective estrogen receptor modulators, such as tamoxifen, are widely used in endocrine therapy. ![]() Compared with ER alpha-negative breast cancer, which is more aggressive and has a shorter survival time, ER alpha-positive breast cancer could benefit from endocrine therapy. More than 70% of breast cancers are estrogen receptor (ER) alpha positive. The homologous region, which is rich in cysteine, lysine, and arginine, may represent the DNA-binding domain of these proteins.īreast cancer is the most common cancer in women worldwide. This suggests that steroid receptor genes and the avian erythroblastosis viral oncogene are derived from a common primordial gene. Amino acid sequence comparisons revealed significant regional homology among the human estrogen receptor, the human glucocorticoid receptor, and the putative v-erbA oncogene product. Interaction of this receptor-estradiol complex with a monoclonal antibody that is specific for primate ER confirms the identity of the expressed complementary DNA as human estrogen receptor. Homogenates of transformed Chinese hamster ovary cells containing a protein that bound estradiol and sedimented as a 4S complex in salt-containing sucrose gradients and as an 8 to 9S complex in the absence of salt. 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. 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. The mechanism by which the estrogen receptor and other steroid hormone receptors regulate gene expression in eukaryotic cells is not well understood.
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