Identification of a Vitamin D Response Element in the Proximal Promoter of the Chicken Carbonic Anhydrase II Gene

Abstract

The carbonic anhydrase II gene, whose transcription is enhanced by 1,25-dihydroxyvitamin D 3 (1,25-(OH) 2 D 3 ), encodes an important enzyme in bone-resorbing cells derived from the fusion of monocytic progenitors. We analyzed the 1,25-(OH) 2 D 3 -mediated activation of the avian gene by transient transfection assays with promoter/reporter constructs into HD11 chicken macrophages and by DNA mobility shift assays. Deletion and mobility shift analyses indicated that the ؊62/؊29 region confers 1,25-(OH) 2 D 3 responsiveness and forms DNA-protein complexes. The addition of an anti-vitamin D receptor (VDR) antibody inhibited binding to this sequence, whereas anti-retinoid X receptor (RXR) antibody generated a lower mobility complex. Therefore, we concluded that this element binds a VDR⅐RXR heterodimer, but the addition of extra 1,25-(OH) 2 D 3 had no effect on the formation of this complex. Moreover, the use of nuclear extracts from 1,25-(OH) 2 D 3 -treated macrophages led to the formation of an additional high mobility complex also composed of VDR⅐RXR heterodimer. Mutations provided evidence that the 1,25-(OH) 2 D 3 -mediated activation of the carbonic anhydrase II gene is mediated by VDR⅐RXR heterodimers bound to a DR3-type vitamin D response element with sequence AGGGCAtggAGTTCG. This vitamin D response element is also functional in the ROS 17/2.8 osteoblasts.Recent work points to the complexity of the molecular mechanisms involved in the vitamin D 3 signaling pathway. It has been known for some time that in addition to the binding of the vitamin D receptor (VDR) 1 to certain vitamin D response elements (VDREs) as homodimer (3-7), the in vitro binding affinity of the VDR is enhanced by dimerization with accessory factors such as RXRs (8 -11). The response elements for these receptors differ from one another by the number of base pairs (bp) spacing the hexameric repeats according to the so-called 1 to 5 rule (1, 2). Following the 1 to 5 rule, optimal VDREs for VDR⅐RXR heterodimers should be direct repeats of two hexameric core binding sites spaced by three nucleotides (DR3) (1, 3). The high specificity of these DR3-type VDREs was confirmed by identification of some natural and synthetic VDREs (10). The mouse osteopontin VDRE has been shown to bind VDR homodimers with low affinity (3, 6, 12, 13) but VDR⅐RXR heterodimers with high affinity (3, 9, 14, 15). DR3-type elements have also been found in numerous promoters such as the rat osteocalcin gene (16,17), the rat calbindin D-9k (18), the avian integrin ␤3 subunit gene (19), the rat 24-hydroxylase gene (20 -22), the avian carbonic anhydrase II (CAII) gene (23), and mouse p21 (24). However, the binding sites of the VDREs characterized so far vary considerably in their sequences, preventing definition of a real VDRE consensus sequence (7,(25)(26)(27).The differentiating effects of 1,25-(OH) 2 D 3 have been studied extensively in a large number of in vitro systems using cultures of leukemia cells (28, 29), keratinocytes (30 -32), or bone cells (33-35). Despite this at...

Novel transcripts of carbonic anhydrase II in mouse and human testis

“…The use of testis-specific alternative promoters located upstream of the 'TATA box' produces extended 5ЈUTR, with the 'TATA box' and other promoter elements incorporated in the additional leader sequence. One of these promoter elements is a vitamin D response element (Quelo et al, 1998) present in the 5ЈUTR of the carbonic anhydrase II transcript expressed in adult chicken testis (Mezquita et al, 1994).…”

Cortisol alters carbonic anhydrase-mediated renal sulfate secretion

“…Several studies suggest that CA expression may be regulated; for example, the avian CAII gene contains a vitamin D 3 response element in the promoter regions (34). Metabolic acidosis in rabbits increases CAII and CAIV activity (6,7,58) and mRNA expression (43,53,58) in the kidney, changes that function to enhance acid excretion.…”

Carbonic anhydrase inhibitors: purification and inhibition studies of pigeon (Columba liviavar.domestica) red blood cell carbonic anhydrase with sulfonamides

“…However, few isozymes of other origin have been investigated in detail. This is particularly true for birds (Aves), for which different reports mention the role of CAs in the eggshell formation for chicken (Gallus gallus) and ostrich (S. camelus), but few attempts have been undertaken to isolate, characterize, and investigate the inhibition of these enzymes were done [15][16][17][18][19][20] . Here, we report on the purification of a CA from pigeon red blood cells as well as on the first inhibition study of this enzyme with a series of aromatic and heterocylic sulfonamides.…”

“…Among birds, the red blood cell enzyme from the ratid Struthio camelus (ostrich) 15 has been investigated in some detail, but as outlined above, these data for enzymes which are of non-human or non-rodent origin, are rather scarce. In the case of birds (Aves), there are several reports on CAs from chicken (Gallus gallus) and ostrich (S. camelus) [16][17][18][19][20] but no attempts were made to isolate, characterize, and study the inhibition of these enzymes were done, except for the ostrich enzyme which has been investigated in detail in this study 15 . It is interesting to note that Thomas 17 reported previously in a preliminary work about some CA activity of pigeon erythrocyte.…”