Regulation of prothymosin alpha gene expression by estrogen in estrogen receptor-containing breast cancer cells via upstream half-palindromic estrogen response element motifs

Endocrinology. 2001 Aug;142(8):3493-501. doi: 10.1210/endo.142.8.8314.

Abstract

Prothymosin alpha (PTalpha), a protein associated with cell proliferation and chromatin remodeling, and found to selectively enhance ER transcriptional activity by interacting with a repressor of ER activity, is shown to be a primary response gene to estrogen. Prothymosin alpha mRNA was rapidly increased by estrogen, followed by a 6-fold increase in prothymosin alpha protein content in ER-containing breast cancer cells. Analysis of the prothymosin alpha promoter and 5'-flanking region, and electrophoretic gel mobility shift studies showed the strong inducibility by the estradiol-ER complex to be mediated by two consensus half-palindromic estrogen response elements at -750 and -1051, which directly bind the ER. Estrogenic stimulation of prothymosin alpha required a DNA binding form of ER with a functional activation function-2 domain. The prothymosin alpha 5'-regulatory region also contains multiple Sp1 sites. Although addition of Sp1 did not further enhance estradiol-ER stimulated prothymosin alpha transcriptional activity in breast cancer cells, transfection and response element mutagenesis studies using Drosophila cells, which are deficient in Sp1, revealed that Sp1 and the estradiol occupied-ER can each activate the prothymosin alpha gene independently of the other and act in an additive manner. These observations, documenting robust prothymosin alpha up-regulation by the estradiol-ER complex via widely spaced half-palindromic estrogen response element motifs, are reminiscent of those shown previously for the ovalbumin gene and suggest that the use of multiple half response elements may be a more common mode for regulation of gene expression by the ER than previously appreciated. In addition, these observations suggest interrelationships between cell proliferation and gene transcriptional activities and indicate a positive mechanism by which PTalpha, which increases ER transcriptional effectiveness, is itself up-regulated by the estrogen-ER complex.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Motifs / physiology*
  • Breast Neoplasms / genetics*
  • Breast Neoplasms / metabolism
  • Estradiol / pharmacology
  • Estrogens / physiology*
  • Gene Expression Regulation, Neoplastic / physiology*
  • Humans
  • Mutagenesis, Site-Directed
  • Promoter Regions, Genetic / drug effects
  • Promoter Regions, Genetic / physiology
  • Protein Precursors / genetics*
  • Protein Precursors / metabolism
  • RNA, Messenger / metabolism
  • Receptors, Estrogen / metabolism*
  • Response Elements / physiology
  • Sp1 Transcription Factor / physiology
  • Thymosin / analogs & derivatives
  • Thymosin / genetics*
  • Thymosin / metabolism
  • Tumor Cells, Cultured
  • Up-Regulation

Substances

  • Estrogens
  • Protein Precursors
  • RNA, Messenger
  • Receptors, Estrogen
  • Sp1 Transcription Factor
  • prothymosin alpha
  • Estradiol
  • Thymosin