Characteristics of the intron involvement in the mitogen-induced expression of Zfp-36.
Zfp-36, the gene encoding the putative zinc finger protein tristetraprolin (TTP), is rapidly induced in fibroblasts by a variety of growth factors. Recent gene knockout experiments have shown that TTP-deficient mice developed arthritis, cachexia, and autoimmunity, all apparently mediated by an excess of tumor necrosis factor alpha. We recently showed that full serum inducibility of Zfp-36 requires elements in the promoter; in addition, removal of the single intron strikingly inhibited serum-induced TTP expression. We show here that replacement of the intron with unrelated sequences, or removal of 95% of the intron but retention of the splice sites, each resulted in the maintenance of approximately 45 and 19%, respectively, of full serum-induced expression. In addition, deletion of intron sequences base pairs 601-655 decreased the serum-induced expression of TTP by 65%. Sequence base pairs 618-626 bound specifically to the transcription factor Sp1; mutation of this binding motif decreased TTP expression by 70%, suggesting that Sp1 binding to this motif contributes to serum induction of Zfp-36. We conclude that full serum-induced expression of Zfp-36 depends on the activation of conventional promoter elements as well as elements in the single intron, and that the presence per se of the intron in its natural location also contributes significantly to the regulated expression of this gene.
Lai
W S
WS
Howard Hughes Medical Institute Laboratories, Section of Diabetes and Metabolism, Division of Endocrinology, Metabolism and Nutrition and the Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
Thompson
M J
MJ
Blackshear
P J
PJ
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001769:Blood; D002478:Cells, Cultured; D002642:Chick Embryo; D004247:DNA; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation / Q000187:drug effects*; D017874:Immediate-Early Proteins; D007438:Introns; D051379:Mice; D008934:Mitogens / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D011485:Protein Binding; D011506:Proteins / Q000235:genetics*; D016329:Sp1 Transcription Factor / Q000378:metabolism; D051816:Tristetraprolin
D004268:DNA-Binding Proteins; D017874:Immediate-Early Proteins; D008934:Mitogens; D016328:NF-kappa B; D011506:Proteins; D016329:Sp1 Transcription Factor; D051816:Tristetraprolin; C497553:Zfp36 protein, mouse; D004247:DNA