Inhibition of laminin-5 production in breast epithelial cells by overexpression of p300

Kristi A. Miller, Jean Chung, David Lo, Jonathan C R Jones, Bayar Thimmapaya, Sigmund A. Weitzman*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


The transcriptional coactivator p300 is essential for normal embryonic development and cellular differentiation. We have been studying the role of p300 in the transcription of a variety of genes, and we became interested in the role of this coactivator in the transcription of genes important in breast epithelial cell biology. From MCF-10A cells (spontaneously immortalized, nontransformed human breast epithelial cells), we developed cell lines that stably overexpress p300. These p300-overexpressing cells displayed reduced adhesion to culture dishes and were found to secrete an extracellular matrix deficient in laminin-5. Laminin-5 is the major extracellular matrix component produced by breast epithelium. Immunofluorescence studies, as well as experiments using normal matrix, confirmed that the decreased adhesion of p300-overexpressing cells is due to laminin-5-deficient extracellular matrix and not due to loss of laminin-5 receptors. Northern blots revealed markedly decreased levels of expression of two of the genes (designated LAMA3 and LAMC2) encoding the a3 and γ2 chains of the laminin-5 heterotrimer in the cells that overexpress p300, whereas LAMB3 mRNA, encoding the third or β3 chain of laminin-5, was not markedly reduced. Transient transfection experiments with a vector containing a murine LAMA3 promoter demonstrate that overexpressing p300 down-regulates the LAMA3 promoter. In summary, overexpression of p300 leads to down-regulation of laminin-5 production in breast epithelial cells, resulting in decreased adhesion.

Original languageEnglish (US)
Pages (from-to)8176-8182
Number of pages7
JournalJournal of Biological Chemistry
Issue number11
StatePublished - Mar 17 2000

ASJC Scopus subject areas

  • Molecular Biology
  • Biochemistry
  • Cell Biology


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