Differential Regulation of Coproporphyrinogen Oxidase Gene Between Erythroid and Nonerythroid Cells

Abstract

Coproporphyrinogen oxidase (CPO) catalyzes the sixth step of the heme biosynthetic pathway. To assess the tissue-specific regulation of the CPO gene promoter, mouse genomic DNA clones for CPO were isolated. Structural analysis demonstrated that the mouse CPO gene spans approximately 11 kb and consists of seven exons, just like its human counterpart. Functional analysis of the promoter by transient transfection assays indicated that synergistic action between an SP-1–like element at −21/−12, a GATA site at −59/−54, and a novel regulatory element, CPRE (-GGACTACAG-) at −49/−41, is essential for the promoter activity in murine erythroleukemia (MEL) cells. In nonerythroid NIH3T3 cells, however, the GATA site is not required. Gel mobility shift assays demonstrated that specific DNA-protein complexes can be formed with each element, and that there are cell-specific differences in factors, which bind to the SP-1–like element between MEL and NIH3T3 cells. These results provide evidence for differential regulation of the promoter function of CPO gene between erythroid and nonerythroid cells. © 1998 by The American Society of Hematology.

Expression of coproporphyrinogen oxidase and synthesis of hemoglobin in human erythroleukemia K562 cells

“…These binding sequences are found in the regulatory regions of the globin genes [31]. Recently, we [11] reported that the regulatory element of the mouse CPOX gene contains three major elements; a GATA site, an Sp-1-like element, and a novel positive cis-regulatory element CPRE, and found that synergistic interaction of these elements is required for CPOX gene expression in erythroid-induced MEL cells. CPRE is not only conserved between mouse and human CPOX genes, but also found in the promoter region of the heme-biosynthetic enzymes including human ALAS2 and b-globin genes [11].…”

“…Recently, we [11] reported that the regulatory element of the mouse CPOX gene contains three major elements; a GATA site, an Sp-1-like element, and a novel positive cis-regulatory element CPRE, and found that synergistic interaction of these elements is required for CPOX gene expression in erythroid-induced MEL cells. CPRE is not only conserved between mouse and human CPOX genes, but also found in the promoter region of the heme-biosynthetic enzymes including human ALAS2 and b-globin genes [11]. Very recently, we isolated a human CPRE-binding protein Klp1, which increases CPOX expression, as assessed by a transcriptional reporter assay, and is abundantly expressed in K562 cells [32].…”

“…Expression of CPOX is weak in hepatic cells and uninduced MEL cells [10], but the enzyme is markedly induced at the transcriptional level during Me 2 SO-mediated differentiation of MEL cells [10]. We [11] found that the regulatory elements of the mouse and human CPOX gene consist of an Sp-1 like element, GATA-1, and a unique CPOX gene promoter regulatory element (CPRE), and synergistic interaction of all three elements is required in the expression of the CPOX gene during erythroid differentiation of MEL cells. Furthermore, CPOX has been reported to become ratelimiting for heme biosynthesis in erythroid and nonerythroid cells [12,13].…”

Molecular aspects of the inherited porphyrias

“…Coproporphyrinogen oxidase transcripts increase during erythroid cell differentiation. Functional analysis of the promoter of the mouse CPO gene demonstrated that synergistic action of an Sp‐1‐like element, a GATA site and a novel regulatory element CPRE (CPO promoter regulatory element) is a prerequisite for the promoter activity in erythroid cells [12]. In contrast, in non‐erythroid cells, the GATA site is not required, whilst CPRE is necessary.…”

“…In contrast, in non‐erythroid cells, the GATA site is not required, whilst CPRE is necessary. These findings indicate that regulation of CPO gene expression is tissue‐specific [12].…”