Organization of the mouse microfibril-associated glycoprotein-2 (MAGP-2) gene

A 1.4-kb EST clone encoding mouse microfibril-associated glycoprotein-2 (MAGP-2), identified by its similarity with the reported human cDNA, was used to screen a mouse 129 genomic bacterial artificial chromosome (BAC) library. The mouse gene contains 10 exons spanning 16 kb, located on the distal region of Chromosome (Chr) 6. The exons range in size from 24 to 963 bp, with the ATG located in exon 2. The tenth and largest exon contains 817 bp of 3′ untranslated sequence, including a B2 repetitive element. Northern analysis demonstrates abundant expression of MAGP-2 mRNA in skeletal muscle, lung, and heart. Sequence analysis of additional cDNA clones suggests that the two mRNA forms of MAGP-2 in the mouse arise from alternative polyadenylation site usage. The promoter does not contain an obvious TATA box, and the sequence surrounding the start site does not conform to the consensus for an initiator promoter element. Additionally, the mouse promoter contains 22 copies of a CT dinucleotide repeat sequence located ∼155 bp 5′ to exon 1. Received: 27 August 1999 / Accepted: 2 November 1999     

Genomic organization of the cadmium-inducible tandem repeat 25-kDa metallothionein of the oligochaete worm Enchytraeus buchholzi

The terrestric oligochaete worm Enchytraeus buchholzi survives in cadmium (Cd)-polluted environments by aid of its Cd-inducible 25 kDa cysteine-rich protein (CRP). Here, we analyze promoter and structure of the crp gene and compare its relationship to MT genes. The crp gene, approximately 12 kbp long, consists of 10 exons with exons 2 to 9 encoding eight almost identical repeats of predominantly 31 amino acids of the CRP. The introns of the crp gene contain various repetitive elements including retrotransposon-like sequences. The 683-bp promoter of the non-constitutive crp gene exhibits a much higher basal activity than the mouse MT-II promoter in HepG2 cells. Essential for crp promoter activity is the distal region (-683/-521) with a GC box and the proximal region (-308/-8) with the four MREa, b, c, d and AP-1, -2, -3 elements, whereas the central portion (-521/-309) with CAAT box, CRE and a XRE causes promoter repression. The TATA box-, MREc- and the AP-2, -3-containing region are required for high crp promoter activity. Our data support the view that the crp gene is a unique MT-gene and has evolved by exon duplications from a MT-like ancestral gene.