Abstract
Feedback regulation of transcription from the low density lipoprotein (LDL) receptor gene is fundamentally important in the maintenance of intracellular sterol balance. The region of the LDL receptor promoter responsible for normal sterol regulation contains adjacent binding sites for the ubiquitous transcription factor Sp1 and the cholesterol-sensitive sterol regulatory element-binding proteins (SREBPs). Interestingly, both are essential for normal sterolmediated regulation of the promoter. The cooperation by Sp1 and SREBP-1 occurs at two steps in the activation process. SREBP-1 stimulates the binding of Sp1 to its adjacent recognition site in the promoter followed by enhanced stimulation of transcription after both proteins are bound to DNA. In the present report, we have defined the protein domains of Sp1 that are required for both synergistic DNA binding and transcriptional activation. The major activation domains of Sp1 that have previously been shown to be essential to activation of promoters containing multiple Sp1 sites are required for activation of the LDL receptor promoter. Additionally, the C domain is also crucial. This slightly acidic approximately 120-amino acid region is not required for efficient synergistic activation by multiple Sp1 sites or in combination with other recently characterized transcriptional regulators. We also show that Sp1 domain C is essential for full, enhanced DNA binding by SREBP-1. Taken together with other recent studies on the role of Sp1 in promoter activation, the current experiments suggest a unique combinatorial mechanism for promoter activation by two distinct transcription factors that are both essential to intracellular cholesterol homeostasis.
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Selected References
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- Attardi L. D., Tjian R. Drosophila tissue-specific transcription factor NTF-1 contains a novel isoleucine-rich activation motif. Genes Dev. 1993 Jul;7(7B):1341–1353. doi: 10.1101/gad.7.7b.1341. [DOI] [PubMed] [Google Scholar]
- Briggs M. R., Yokoyama C., Wang X., Brown M. S., Goldstein J. L. Nuclear protein that binds sterol regulatory element of low density lipoprotein receptor promoter. I. Identification of the protein and delineation of its target nucleotide sequence. J Biol Chem. 1993 Jul 5;268(19):14490–14496. [PubMed] [Google Scholar]
- Brown M. S., Goldstein J. L. A receptor-mediated pathway for cholesterol homeostasis. Science. 1986 Apr 4;232(4746):34–47. doi: 10.1126/science.3513311. [DOI] [PubMed] [Google Scholar]
- Courey A. J., Holtzman D. A., Jackson S. P., Tjian R. Synergistic activation by the glutamine-rich domains of human transcription factor Sp1. Cell. 1989 Dec 1;59(5):827–836. doi: 10.1016/0092-8674(89)90606-5. [DOI] [PubMed] [Google Scholar]
- Courey A. J., Tjian R. Analysis of Sp1 in vivo reveals multiple transcriptional domains, including a novel glutamine-rich activation motif. Cell. 1988 Dec 2;55(5):887–898. doi: 10.1016/0092-8674(88)90144-4. [DOI] [PubMed] [Google Scholar]
- Dawson P. A., Hofmann S. L., van der Westhuyzen D. R., Südhof T. C., Brown M. S., Goldstein J. L. Sterol-dependent repression of low density lipoprotein receptor promoter mediated by 16-base pair sequence adjacent to binding site for transcription factor Sp1. J Biol Chem. 1988 Mar 5;263(7):3372–3379. [PubMed] [Google Scholar]
- Pascal E., Tjian R. Different activation domains of Sp1 govern formation of multimers and mediate transcriptional synergism. Genes Dev. 1991 Sep;5(9):1646–1656. doi: 10.1101/gad.5.9.1646. [DOI] [PubMed] [Google Scholar]
- Perkins N. D., Agranoff A. B., Pascal E., Nabel G. J. An interaction between the DNA-binding domains of RelA(p65) and Sp1 mediates human immunodeficiency virus gene activation. Mol Cell Biol. 1994 Oct;14(10):6570–6583. doi: 10.1128/mcb.14.10.6570. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Perkins N. D., Edwards N. L., Duckett C. S., Agranoff A. B., Schmid R. M., Nabel G. J. A cooperative interaction between NF-kappa B and Sp1 is required for HIV-1 enhancer activation. EMBO J. 1993 Sep;12(9):3551–3558. doi: 10.1002/j.1460-2075.1993.tb06029.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sanchez H. B., Yieh L., Osborne T. F. Cooperation by sterol regulatory element-binding protein and Sp1 in sterol regulation of low density lipoprotein receptor gene. J Biol Chem. 1995 Jan 20;270(3):1161–1169. doi: 10.1074/jbc.270.3.1161. [DOI] [PubMed] [Google Scholar]
- Sato R., Yang J., Wang X., Evans M. J., Ho Y. K., Goldstein J. L., Brown M. S. Assignment of the membrane attachment, DNA binding, and transcriptional activation domains of sterol regulatory element-binding protein-1 (SREBP-1). J Biol Chem. 1994 Jun 24;269(25):17267–17273. [PubMed] [Google Scholar]
- Smith J. R., Osborne T. F., Goldstein J. L., Brown M. S. Identification of nucleotides responsible for enhancer activity of sterol regulatory element in low density lipoprotein receptor gene. J Biol Chem. 1990 Feb 5;265(4):2306–2310. [PubMed] [Google Scholar]
- Südhof T. C., Russell D. W., Brown M. S., Goldstein J. L. 42 bp element from LDL receptor gene confers end-product repression by sterols when inserted into viral TK promoter. Cell. 1987 Mar 27;48(6):1061–1069. doi: 10.1016/0092-8674(87)90713-6. [DOI] [PubMed] [Google Scholar]
- Südhof T. C., Van der Westhuyzen D. R., Goldstein J. L., Brown M. S., Russell D. W. Three direct repeats and a TATA-like sequence are required for regulated expression of the human low density lipoprotein receptor gene. J Biol Chem. 1987 Aug 5;262(22):10773–10779. [PubMed] [Google Scholar]