Structural organization of the pigment cell-specific gene located at the brown locus in mouse. Its promoter activity and alternatively spliced transcript

Human Melanocytes and Melanomas Express Novel mRNA Isoforms of the Tyrosinase-Related Protein-2/DOPAchrome Tautomerase Gene: Molecular and Functional Characterization

“…This ®nding, together with the evidence by northern blot analysis that melanoma and melanocytes express at least two transcripts of approximately 2.3 and 4.5 kb (Mu Èller et al, 1988;Bouchard et al, 1994;Yokoyama et al, 1994;Sturm et al, 1995) suggested that, beside the single TRP-2 cDNA described so far corresponding to the 2.3 kb species, other mRNA isoforms could exist. Further support to such hypothesis was also provided by the occurrence of alternative processing within the albino and brown loci, the murine homologous of tyrosinase and TRP-1, respectively (Mu Èller et al, 1988;Ruppert et al, 1988;Porter and Mintz, 1991;Shibahara et al, 1991) and within the human D12S53E gene that encodes the melanosomal matrix glycoprotein pMel 17/gp100 (Bailin et al, 1996). Here we report the characterization, from a human melanoma cell line, of two novel transcripts of human tyrosinase-related protein-2/DOPAchrome tautomerase (TRP-2/DT) gene.…”

“…This region is surrounded by sequences required for nuclear pre-mRNA splicing to occur (Reed, 1996;Coolidge et al, 1997), indicating that the new exon we named 8b, is contained within the TRP-2 gene beside the eight already described by Sturm et al, 1995. Therefore, usage of the poly(A) site at the 3¢-end of TRP-2-LT allows exon 7coding sequences to be spliced to either exon 8 or exon 8b, resulting in mRNA transcripts whose open reading frames specify either a 519 or a 477 amino acid protein, respectively. Alternatively spliced forms have been described for murine TRP-1 and tyrosinase gene (Mu Èller et al, 1988;Ruppert et al, 1988;Porter and Mintz, 1991;Shibahara et al, 1991) and for the human D12S53E locus where nuclear processing yields, as result of alternative usage of two different 3¢ acceptor sites, two transcripts encoding melanosomal matrix proteins of 661 (gp100) or 668 (pMel17) amino acids in lengths differing only for an in-frame 21 bp deletion/insertion (Bailin et al, 1996).…”

“…As TRP-2±8b lacks exon 8 that contains the putative transmembrane domain (Yokoyama et al, 1994;Bouchard et al, 1994;Cassady and Sturm, 1994), it should not be able to bind the melanosomal membrane and could therefore represent a soluble version of TRP-2. Two soluble forms generated either by posttranslational proteolytic degradation or by alternative splicing have been described for the mouse gp75/TRP-1 (Shibahara et al, 1991;Xu et al, 1997) that, differently from the human TRP-1 protein (Boissy et al, 1998) has been shown to possess, in addition to a tyrosinase stabilizing capacity (Kobayashi et al, 1998), DHICA oxidase activity (Kobayashi et al, 1994). Both forms are devoid of the transmembrane-spanning domain but their function has not been elucidated.…”

Functional Conservation of the Promoter Regions of Vertebrate Tyrosinase Genes

“…In contrast, only a few short sequence motifs are shared in the 5¢ ¯anking regions of mammalian and nonmammalian tyrosinase genes (Tanaka et al, 1992;. The ®rst such motif was an 11 bp element now termed the M-box (Lowings et al, 1992), previously designated as either the upstream element (Shibahara et al, 1991), an 11-mer motif (Jackson et al, 1991), or p-MSE (Yamamoto et al, 1992). This regulatory motif is also found in the proximal promoters of genes encoding the related melanogenic enzymes, tyrosinase-related protein-1 (Tyrp1) and tyrosinase-related protein-2 or dopachrome tautomerase (Dct) (Jackson et al, 1991;Shibahara et al, 1991;Lowings et al, 1992;Yamamoto et al, 1992;Yokoyama et al, 1994;Budd and Jackson, 1995;Miura et al, 1995;Ferguson and Kidson, 1996).…”

“…The ®rst such motif was an 11 bp element now termed the M-box (Lowings et al, 1992), previously designated as either the upstream element (Shibahara et al, 1991), an 11-mer motif (Jackson et al, 1991), or p-MSE (Yamamoto et al, 1992). This regulatory motif is also found in the proximal promoters of genes encoding the related melanogenic enzymes, tyrosinase-related protein-1 (Tyrp1) and tyrosinase-related protein-2 or dopachrome tautomerase (Dct) (Jackson et al, 1991;Shibahara et al, 1991;Lowings et al, 1992;Yamamoto et al, 1992;Yokoyama et al, 1994;Budd and Jackson, 1995;Miura et al, 1995;Ferguson and Kidson, 1996). Functional analyses of mammalian tyrosinase proximal promoters identi®ed the M-box as a positive regulatory element for melanocyte-speci®c expression (Bentley et al, 1994;Ganss et al, 1994c;Yasumoto et al, 1997).…”