Purification of a novel factor which binds to the mouse alpha 2 (I) collagen promoter

The transcription of human alpha 1(I) procollagen gene (COL1A1) is suppressed by tumour necrosis factor-alpha through proximal short promoter elements: evidence for suppression mechanisms mediated by two nuclear-factorbinding sites

Recent studies have demonstrated that tumour necrosis factor-alpha (TNF-alpha) decreases alpha 1(I) procollagen gene (COL1A1) expression in cultured human dermal fibroblasts. The purpose of this study was to analyse the transcriptional control of COL1A1 by TNF-alpha. Cultured human dermal fibroblasts were transiently transfected with plasmids containing 5' flanking sequences of COL1A1 fused to the chloramphenicol acetyltransferase (CAT) gene, and were incubated for 48 h in medium with or without TNF-alpha. TNF-alpha inhibited the CAT activity of fibroblasts transfected with plasmids containing 2.3 kb of 5' flanking sequences of COL1A1, whereas the activity of control plasmids containing the herpes simplex thymidine kinase promoter gene (pBLCAT) was unaltered. A series of deletion constructs of various small substitution mutations of the COL1A1 5' flanking region fused to the CAT gene were also transfected, and CAT activity was measured after incubation with TNF-alpha. TNF-alpha suppressed COL1A1 promoter activity through proximal short promoter elements containing only 107 bp. Short substitution mutations between -101 and -97 bp or between -46 and -38 bp abolished TNF-alpha suppression of COL1A1 promoter activity. DNA-protein complex formation was observed involving both sites in gel retardation assays. These results suggest that TNF-alpha suppressed COL1A1 promoter activity through elements located between -101 and -97 bp and between -46 and -38 bp of the COL1A1 promoter, and that the suppression involved DNA-protein interactions.

Transcriptional regulation of the human alpha2(I) collagen gene. Combined action of upstream stimulatory and inhibitory cis-acting elements

This study identifies three regions of the human alpha2(I) collagen promoter involved in the binding of nuclear factors. These regions include sequences from -173 to -155 (footprint I), -133 to -119 (footprint II), and -101 to -72 (footprint III). A novel positive cis-element containing a TCCTCC motif was identified within footprint II. In addition, we demonstrated that a pyrimidine-rich region within footprint I is a binding site for a transcriptional repressor, and a CCAAT motif within footprint III is a binding site for a transcriptional activator. Comparative functional analysis of the cis-acting elements within the proximal 350 base pairs of this promoter, including previously characterized Sp1 binding sites at -300, indicates that constitutive activity of this promoter is regulated equivalently by the three positive cis-acting elements at -300, -125, and -80. Mutations in the repressor site at -160 increase constitutive activity by 4-6-fold. However, simultaneous mutations of the repressor site and the cis-regulatory element at either the -300 or -125 sites result in no increase in constitutive transcription activity suggesting interaction between the activators and repressor elements. In contrast, simultaneous mutation of the CCAAT motif and the repressor site results in about a 4-fold increase, suggesting that activation via the CCAAT motif may be independent of this repressor.

Involvement of a protein distinct from transcription enhancer factor-1 (TEF-1) in mediating human chorionic somatomammotropin gene enhancer function through the GT-IIC enhanson in choriocarcinoma and COS cells

Previous studies suggested that transcription enhancer factor-1 (TEF-1) was involved in mediating the human chorionic somatomammotropin (hCS) gene enhancer (CSEn) function (Jiang, S.-W., and Eberhardt, N. L. (1994) J. Biol. Chem. 269, 10384-10392). We now show that an unrelated protein (CSEF-1) found in BeWo and COS-1 cells binds to the GT-IIC enhanson in CSEn and is correlated with CSEn activity in these cells. TEF-1 and CSEF-1 were distinguished by differential migration as GT-IIC complexes, thermal stability, molecular mass, and cross-reactivity with chicken TEF-1 antibodies. TEF-1 and CSEF-1 bound to the GT-IIC and Sph-I/Sph-II enhansons with identical binding properties, and in vitro generated TEF-1 competed with CSEF-1 binding to the GT-IIC motif, suggesting that their actions might be mutually exclusive. Up- and down-regulation of TEF-1 levels by expression systems and antisense oligonucleotides demonstrated that TEF-1 inhibited the hCS promoter in a manner independent of the enhancer or a known TEF-1 DNA binding site. The data suggest that TEF-1 may provide a counter-regulatory stimulus to the actions of CSEF-1, which may be involved in mediating enhancer stimulatory activity.

Cell-type specific promoters of the chick alpha 2(I) collagen gene in chondrocytes and fibroblasts

Two different promoter regions responsible for the cell-type specific transcripts of the collagen alpha 2(I) gene in chick embryonic fibroblasts and chondrocytes are described. A region including part of intron 1 of the fibroblast alpha 2(I) gene is able to promote transcription in chondrocytes. This promoter region is located 5' to the chondrocyte-specific transcript, from -2205 to +42, relative to the chondrocyte transcription start site. When it is placed upstream of a luciferase reporter gene in transiently transfected chondrocytes, luciferase activity is stimulated 78-fold. The region between -2205 and -1298 is most important for the activity of the chondrocyte promoter, since a truncated promoter from -1298 through +42 gives only 15% as much activity. A similar low level of activity is given by the sequence -96 through +42. In transfected fibroblasts, a region from -1600 through +46, relative to the fibroblast transcription start site, stimulates transcription of a luciferase reporter gene by more than 1,000-fold. Deletions from -1185 through -807 and from -707 through -90 reduce promoter activity to 22% and 32%, respectively, of that given by the intact promoter. The chondrocyte and fibroblast promoters are each cell-type specific and are relatively inactive in the other cell type. Subregions within the fibroblast promoter, from -1154 through -1055, from -712 through -85, and the sequence containing the inverted CCAAT motif from -93 through -67, differentially bind factors in fibroblast but not chondrocyte nuclear extracts.