Subject(s)
Ascorbic Acid/pharmacology , Avian Proteins , Carrier Proteins/biosynthesis , Cartilage/metabolism , Cytokines , 2,2'-Dipyridyl/pharmacology , Animals , Carrier Proteins/drug effects , Carrier Proteins/genetics , Carrier Proteins/metabolism , Cartilage/cytology , Cell Differentiation , Cells, Cultured , Chick Embryo , Extracellular Matrix/metabolism , Gene Expression , Glycerophosphates/pharmacology , Intracellular Signaling Peptides and Proteins , Midkine , Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase/metabolism , Procollagen-Proline Dioxygenase/metabolism , RNA, MessengerABSTRACT
The human homeobox protein EVX1 (EVX1) is thought to play an important role during embryogenesis. In this study, the effect of EVX1 on gene transcription has been investigated in transfected mammalian cells. EVX1 expression represses transcription of a reporter gene directed by either cell-specific or viral promoter/enhancer sequences in a variety of mammalian cell lines and in a concentration-dependent manner. Transcriptional repression is independent of the presence of DNA-binding sites for EVX1 in all the promoters we tested. Furthermore, repression by EVX1 is evident also using a TATA-less minimal promoter in the reporter construct. A carboxyl-terminal proline/alanine-rich region of EVX1 seems to be responsible for the transcriptional repression activity, as suggested by transfection of EVX1 mutants. We speculate that the repressor function of EVX1 contributes to its proposed role in embryogenesis.
Subject(s)
Homeodomain Proteins/metabolism , Transcription, Genetic , Animals , Cell Nucleus/metabolism , Chloramphenicol O-Acetyltransferase/analysis , Chloramphenicol O-Acetyltransferase/biosynthesis , Cricetinae , Fluorescent Antibody Technique , HeLa Cells , Homeodomain Proteins/biosynthesis , Homeodomain Proteins/isolation & purification , Humans , Immunohistochemistry , Mammals , Mice , Plasmids , Promoter Regions, Genetic , Recombinant Proteins/biosynthesis , Recombinant Proteins/isolation & purification , Recombinant Proteins/metabolism , TATA Box , Teratocarcinoma , Transfection , Tumor Cells, CulturedABSTRACT
It has been proposed that tensin, in association with several other proteins, mediates the micro-filament-integrin link. Here we describe the isolation of clones spanning about 5 kb from the 3' end of tensin mRNA from cultured chick embryo chondrocyte and embryonic heart cDNA libraries. Tensin expression was investigated in cultured chick embryo cells. It was observed that tensin expression is dependent upon substrate adhesion and it is turned off after 7 days of suspension culture. This process is reversible. Tensin expression is also regulated during cartilage cell differentiation in vivo; at Hamburger and Hamilton stage 39-40, non-hypertrophic tibial chondrocytes express both RNA and protein while hypertrophic chondrocytes do not. In the culture system the expression of vimentin, a major component of intermediate filaments, showed an opposite behaviour since the suspension culture enhances the accumulation of both vimentin and its mRNAs. Therefore in chick embryo cultured chondrocytes and in vivo, during cartilage development, cell shape changes and/or integrin-extracellular matrix protein interactions may be involved in the regulation of these two genes coding for cytoskeletal proteins.
