title: Potentiation of human estrogen receptor alpha transcriptional activation through phosphorylation of serines 104 and 106 by the cyclin A-CDK2 complex.
abstract: Both estradiol binding and phosphorylation regulate transcriptional activation by the human estrogen receptor alpha (ER). We have previously shown that activation of the cyclin A-CDK2 complex by overexpression of cyclin A leads to enhanced ER-dependent transcriptional activation and that the cyclin A-CDK2 complex phosphorylates the ER N-terminal activation function-1 (AF-1) between residues 82 and 121. Within ER AF-1, serines 104, 106, and 118 represent potential CDK phosphorylation sites, and in this current study, we ascertain their importance in mediating cyclin A-CDK2-dependent enhancement of ER transcriptional activity. Cyclin A overexpression does not enhance transcriptional activation by an ER derivative bearing serine-to-alanine changes at residues 104, 106, and 118. Likewise, the cyclin A-CDK2 complex does not phosphorylate this triple-mutated derivative in vitro. Individual serine-to-alanine mutations at residues 104 and 106, but not 118, decrease ER-dependent transcriptional enhancement in response to cyclin A. The same relationship holds for ER phosphorylation by cyclin A-CDK2 in vitro. Finally, enhancement of ER transcriptional activation by cyclin A is evident in the absence and presence of estradiol, as well as in the presence of tamoxifen, suggesting that the effect of the cyclin A-CDK2 on ER transcriptional activation is AF-2-independent. These results indicate that the enhancement of ER transcriptional activation by the cyclin A-CDK2 complex is mediated via the AF-1 domain by phosphorylation of serines 104 and 106. We propose that these residues control ER AF-1 activity in response to signals that affect cyclin A-CDK2 function.
authors.affiliation: Department of Microbiology and the Kaplan Comprehensive Cancer Center, New York University School of Medicine, New York, New York 10016, USA.
authors.forename: I
authors.initials: I
authors.lastname: Rogatsky
authors.forename: J M
authors.initials: JM
authors.lastname: Trowbridge
authors.forename: M J
authors.initials: MJ
authors.lastname: Garabedian
mesh_terms: D042846:CDC2-CDC28 Kinases; D019925:Cyclin A / Q000235:genetics / Q000378:metabolism*; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004958:Estradiol / Q000378:metabolism; D047628:Estrogen Receptor alpha; D006801:Humans; D008957:Models, Genetic; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D019925:Cyclin A; D047628:Estrogen Receptor alpha; D011960:Receptors, Estrogen; D011994:Recombinant Proteins; D012694:Serine; D004958:Estradiol; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases