Characterization of BCE-1, a Transcriptional Enhancer Regulated by Prolactin and Extracellular Matrix and Modulated by the State of Histone Acetylation
| Autor: | Calvin D. Roskelley, Gilberto Fragoso, Julia Mellentin-Michelotti, Mina J. Bissell, Connie A. Myers, Christian Schmidhauser, Philippe Pujuguet, Gordon L. Hager, Gerald F. Casperson, Romina Mossi |
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| Jazyk: | angličtina |
| Rok vydání: | 1998 |
| Předmět: |
Transcriptional Activation
Integrin Molecular Sequence Data Biology Transfection Histone Deacetylases Cell Line Histones Gene expression Transcriptional regulation STAT5 Transcription Factor Animals Enhancer Molecular Biology Sequence Deletion Regulation of gene expression Transcriptional Regulation Reporter gene Base Sequence Caseins Nuclear Proteins Promoter Acetylation Cell Biology DNA Templates Genetic Milk Proteins Molecular biology Chromatin Extracellular Matrix Prolactin DNA-Binding Proteins Histone Deacetylase Inhibitors Enhancer Elements Genetic Gene Expression Regulation biology.protein CCAAT-Enhancer-Binding Proteins Mutagenesis Site-Directed Trans-Activators Cattle Electrophoresis Polyacrylamide Gel Signal transduction Protein Binding |
| Popis: | It is now well established that the processes of development and differentiation depend on a cell’s ability to correctly perceive its microenvironment (reviewed in references 1 and 43). A key component of this environment is the extracellular matrix (ECM). The ECM is an organized network of glycoproteins, proteoglycans, and glycosaminoglycans, components important for cell morphology as well as for signal transduction via cell surface integrins and ultimately for tissue-specific gene expression (reviewed in reference 43). The mammary gland appears to be particularly well suited for the study of ECM-induced differentiation and gene expression. In the adult animal, the gland develops after puberty and functionally differentiates in response to pregnancy. The mechanisms involved in these developmental processes are complex and guided by various hormones (54), growth factors (53), and the ECM (3). Milk protein expression is initiated at mid-pregnancy and correlates with the synthesis and deposition of a specialized laminin-rich ECM during alveolar development. Expression of these milk proteins can be used as markers for the differentiated state of the gland. In the last decade, a number of model systems using mammary epithelial cells to study ECM-dependent gene regulation have been developed. These range from primary cultures to cloned cell lines which undergo a three-dimensional reorganization in gelatinous matrices to form alveolus-like structures capable of synthesizing and vectorially secreting milk proteins, analogous to their in vivo counterparts in the lactating mammary gland (references 2 and 30 and references therein). Studies with SCP2 (11) and CID-9 (44) cell lines derived from the COMMA 1D cell strain (8), itself derived from the mammary tissue of midpregnancy mice, have shown that induction of endogenous β-casein requires both an ECM-induced change in cell shape and a β1-integrin-mediated biochemical signaling by laminin, a major component of mammary basement membrane (42, 52). Downstream nuclear events associated with this integrin signal transduction pathway have been analyzed with stable transfectants of CID-9 cells with the bovine β-casein promoter linked to the chloramphenicol acetyltransferase (CAT) reporter gene. These studies clearly demonstrated that the transcriptional regulation of this gene is dependent on the presence of both ECM and lactogenic hormones (44). Deletion analysis of this promoter identified a 160-bp transcriptional enhancer (BCE-1) capable of conferring ECM and hormonal regulation in either orientation to the inactive proximal β-casein promoter (−121 to +42) (46). Many cis-acting transcription elements have been identified in the rat and mouse β-casein genes. Their functional role in induction of transcription has been studied in mammary glands of transgenic animals, in primary mammary epithelial cells, and in other cell lines such as HC11 (also derived from COMMA 1D) (14, 19, 29, 63). These studies have identified three major trans-acting factors that are involved in the hormone-induced transcriptional activation of β-casein. Prolactin has been shown to activate transcription via STAT5, originally identified as mammary gland factor (MGF) (20, 47, 56, 57–59). STAT5 binding sites are found in many other milk protein promoters, with the STAT binding sites in the sheep β-lactoglobulin gene being particularly well characterized (5, 6, 51, 58). C/EBP binding sites are required for the hormonal induction of β-casein expression (16, 41, 49), and its activity may be influenced by glucocorticoid receptor, which has been shown to enhance prolactin-induced expression of β-casein (15, 25, 41, 44, 50). In this study, we found that the binding sites for C/EBP and STAT5 are contained within the ECM-responsive element BCE-1. Furthermore, we show that these elements, as well as an unidentified binding protein (UBP) site are critical for ECM and prolactin responsiveness. Unexpectedly, we also find that despite the dramatic increase in transcription when the cells are cultured on ECM, these factors appear to be bound to BCE-1 even when cells are cultured on plastic in the absence of prolactin. Based on the induction of BCE-1 transcriptional activity in cells cultured on plastic after treatment with histone deacetylase inhibitors, we propose that the ECM may allow transcription of the β-casein gene via a mechanism that involves modulation of histone acetylation. |
| Databáze: | OpenAIRE |
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