N-terminal activation function is dominant in ligand-dependent transactivation of medaka estrogen receptor alpha in human cells.
Two independent transcriptional activation functions have been mapped to the N- and C-terminal domains of estrogen receptors (ERs), and are named activation function-1 (AF-1) and AF-2, respectively. Due to the lower activity of AF-1 and difficulties in producing AF-1 recombinant protein, little information is available regarding the biochemical properties of ER AF-1 and its coactivators compared to AF-2. In this study, we characterized the AF domains from medaka fish ERalpha (meERalpha) using a transient expression assay in cultured mammalian cells. While both meERalpha AF-1 and AF-2 were functional and gave similar results to human ERalpha AFs, meERalpha AF-1 displayed significant activity even in HeLa cells that exhibit little human ERalpha (hERalpha) AF-1 activity. Evidence of transcriptional squelching between hERalpha and meERalpha AF-1 molecules suggested that the molecules utilized common coactivators in mammalian cells. We also showed that large amounts of the meERalpha A/B domain could be expressed in Escherichia coli cells as a soluble protein, in contrast to hERalpha A/B domain protein which was not observed. Taken together, our results suggested that meERalpha AF-1 may have a more significant role in estrogen-induced function of meERalpha than AF-2 in medaka fish.
Mezaki
Y
Y
Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
Yoshida
T
T
Yanagisawa
J
J
Kato
S
S
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002645:Chickens; D004926:Escherichia coli / Q000235:genetics; D047628:Estrogen Receptor alpha; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D008024:Ligands; D008969:Molecular Sequence Data; D009990:Oryzias / Q000235:genetics*; D017434:Protein Structure, Tertiary; D011960:Receptors, Estrogen / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D015533:Transcriptional Activation; D014162:Transfection; D014981:Xenopus
D047628:Estrogen Receptor alpha; D008024:Ligands; D011960:Receptors, Estrogen; C442419:estrogen receptor alpha, medaka