Open AccessTranscriptional activation of the α1(I) procollagen gene and up‐regulation of α1(I) and α1(III) procollagen messenger RNA in dermal fibroblasts from tight skin 2 mice
Author(s) -
Christner Paul J.,
Hitraya Elena G.,
Peters Josephine,
McGrath Rodney,
Jiménez Sergio A.
Publication year - 1998
Publication title -
arthritis & rheumatism
Language(s) - English
Resource type - Journals
eISSN - 1529-0131
pISSN - 0004-3591
DOI - 10.1002/1529-0131(199812)41:12<2132::aid-art8>3.0.co;2-w
Subject(s) - procollagen peptidase , microbiology and biotechnology , messenger rna , electrophoretic mobility shift assay , gene expression , transfection , transcriptional regulation , fibroblast , reporter gene , rna , biology , regulation of gene expression , gene , northern blot , chemistry , cell culture , biochemistry , genetics
Objective To investigate the levels of expression of type I and type III collagen genes in dermal fibroblasts from tight skin 2 ( Tsk2 ) and normal mice and to examine the transcriptional regulation of the α1(I) procollagen gene (COL1A1) in these cells. Methods Dermal fibroblasts from Tsk2 mice and from normal age‐ and sex‐matched control mice were studied. Steady‐state levels of α1(I) and α1(III) procollagen messenger RNA (mRNA) were evaluated by Northern and dot‐blot hybridization analyses. The transcriptional regulation of COL1A1 was examined by transient transfection experiments with deletion constructs containing portions of the COL1A1 promoter ligated to the chloramphenicol acetyltransferase reporter gene. To identify DNA binding proteins that interact with regulatory elements within the COL1A1 promoter, gel mobility shift assays were performed with nuclear extracts prepared from normal and Tsk2 dermal fibroblasts. Results Synthesis of collagen was almost 100% higher in Tsk2 dermal fibroblasts than in control fibroblasts. Up‐regulation of mRNA for 2 extracellular matrix proteins was observed in the Tsk2 dermal fibroblasts compared with the normal cells: the α1(I) procollagen mRNA steady‐state levels were 50% higher, and those of the α1(III) procollagen mRNA 100% higher, in Tsk2 cells. The results of transient transfection experiments with COL1A1 promoter constructs demonstrated that the elevated levels of α1(I) collagen mRNA in Tsk2 cells were largely due to increased transcriptional activity of the corresponding gene. Electrophoretic mobility shift assays performed with a probe encompassing a relevant COL1A1 promoter region revealed increased DNA‐protein binding activities in nuclear extracts prepared from Tsk2 fibroblasts compared with normal fibroblasts. Competition experiments using consensus Sp1 and nuclear factor 1 (NF‐1) oligonucleotides and supershift experiments using anti‐Sp1 and anti‐NF1 antibodies indicated that at least 2 transcription factors, Sp1 and NF‐1, or their homologs are involved in the up‐regulated transcriptional activity of the COL1A1 promoter in Tsk2 fibroblasts. Conclusion Dermal fibroblasts from Tsk2 mice display increased collagen synthesis and up‐regulation of α1(I) and α1(III) procollagen mRNA in vitro. The data also directly demonstrate the transcriptional activation of COL1A1 in dermal fibroblasts from Tsk2 mice and suggest that the transcriptional factors Sp1 and NF‐1 or their homologs play an important role in the up‐regulated expression of this gene in Tsk2 fibroblasts. These findings are similar to those described for fibroblasts from humans with systemic sclerosis and validate the use of Tsk2 as a model for the study of the connective tissue alterations in this disease.