title: Inhibition of laminin-5 production in breast epithelial cells by overexpression of p300.
abstract: 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 alpha3 and gamma2 chains of the laminin-5 heterotrimer in the cells that overexpress p300, whereas LAMB3 mRNA, encoding the third or beta3 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.
authors.affiliation: Department of Medicine, Division of Hematology/Oncology, Northwestern University Medical School, Chicago, Illinois 60611, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Miller
authors.forename: J
authors.initials: J
authors.lastname: Chung
authors.forename: D
authors.initials: D
authors.lastname: Lo
authors.forename: J C
authors.initials: JC
authors.lastname: Jones
authors.forename: B
authors.initials: B
authors.lastname: Thimmapaya
authors.forename: S A
authors.initials: SA
authors.lastname: Weitzman
mesh_terms: D001940:Breast / Q000166:cytology / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000096:biosynthesis*; D002478:Cells, Cultured; D015536:Down-Regulation; D004847:Epithelial Cells / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007797:Laminin / Q000235:genetics; D009687:Nuclear Proteins / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000096:biosynthesis*; D000097794:Kalinin
chemical_list: D015815:Cell Adhesion Molecules; D016326:Extracellular Matrix Proteins; D007797:Laminin; D009687:Nuclear Proteins; D015534:Trans-Activators; D000097794:Kalinin; C095567:laminin alpha 3