Identification of a Second Region Upstream of the Mouse Heme Oxygenase-1 Gene That Functions as a Basal Level and Inducer-dependent Transcription Enhancer

Abstract

A 161-base pair fragment (AB1) approximately 10 kilobase pairs upstream of the transcription start site of the mouse heme oxygenase-1 gene functions as a basal level and inducer-dependent enhancer. AB1/chloramphenicol acetyltransferase fusion genes stably transfected into mouse hepatoma (Hepa) cells or L929 fibroblasts were activated 7-8- or 17-22-fold, respectively, after treatment of the cells with either CdCl2 or heme. The AB1 fragment is composed largely of three tandem repeats containing two conserved core elements, A and B. Part of core element A (TCCGGAGCTGTG) resembles the consensus-binding site for transcription factor AP-4, whereas core element B (GCTGAGTCANGG) includes the consensus-binding site (TGAGTCA) for the AP-1 family of transcription factors. Nuclear proteins from Hepa cells did not bind to any of the core A elements, but bound to all three copies of the core B element. AB1 derivatives with one or two mutant AP-1-binding elements exhibited reduced but measurable inducer-dependent enhancer activity, but mutation of all three AP-1-binding sites abolished activation by CdCl2 and heme and also by mercury chloride, zinc chloride, H2O2, sodium arsenate, and 12-O-tetradecanoylphorbol-13-acetate. Pretreatment of stably transfected L929 cells with protein kinase C inhibitors, but not with tyrosine kinase inhibitors or N-acetylcysteine, abrogated 12-O-tetradecanoylphorbol-13-acetate-dependent activation of the AB1/chloramphenicol acetyltransferase fusion gene. Induction by H2O2 was unaffected by the kinase inhibitors, but completely abolished by N-acetylcysteine. Heme-dependent induction was not significantly affected by any of these chemicals.

Hypothetical mode of action of earthworm extract with hepatoprotective and antioxidant properties

“…Further, Alum et al(1995) have shown HO-1 gene to be induced by reactive oxygen species like H 2 O 2 and singlet oxygen ( 1 O 2 ) which set the reduction reaction leading to enhanced bilirubin content. It is known that both biliverdin and bilirubin exhibit antioxidant properties.…”

TGF-β1stimulates HO-1 via the p38 mitogen-activated protein kinase in A549 pulmonary epithelial cells

“…Here we determined the ability of TGF-␤ 1 to activate the transcription of an ho-1 promoter/luciferase reporter fusion gene containing the 33-bp HO-1 minimal promoter sequences and the 268-bp HO-1 enhancer SX2, previously identified as a mediator of ho-1 gene activation by a variety of stimuli in A549 cells (2,3). Furthermore, in A549 cells, treatment with actinomycin D, which inhibits transcription, attenuated the ability of TGF-␤ 1 to induce HO-1 mRNA.…”

“…The p38 MAPK pathway was blocked either by the selective chemical inhibition of p38 MAPK with SB-203580 or by genetic blockade with a dominant-negative mutant of p38 MAPK. HO-1 promoter activity was assessed by transfection of a luciferase reporter construct (pMHO1luc-33ϩSX2) containing the 33-bp HO-1 minimal promoter sequences and the 268-bp HO-1 enhancer SX2, previously identified as a mediator of ho-1 gene activation by a variety of stimuli (2,3). As shown in Fig.…”

Involvement of protein kinase in Δ12‐prostaglandin J2‐induced expression of rat heme oxygenase‐1 gene

“…Concerning regulatory mechanism for stress protein induction, a cDNA for a novel serine/threonine kinase, Ern lp, has been recently isolated from yeast, and this kinase was shown to be essential for a set of specific stress gene expression induced by perturbation of nascent protein synthesis [25,26]. The A 12-PGJ 2-induced HSP70 gene expression has been shown to require de novo protein synthesis [22,23]. The A12-PGJ2-induced HO-I gene expression also required de novo protein synthesis (data not shown).…”