In order to explore the Sec2 gene of a Japanese population, we performed a molecular genetic analysis of the Sec2 gene on 226 Japanese individuals, 21 in a family study and 205 in a random sampling study. We discovered two novel mutations in the Sec2 gene, an A385T missense mutation (Ile 129 to Phe) that results in inactivation of Sec2-encoded ␣(1,2)fucosyltransferase and a C357T silent mutation which is irrelevant to amino acid substitution, in Japanese nonsecretors.The analysis of Japanese individuals using the polymerase chain reaction-restriction fragment length polymorphism method found three alleles in the Sec2 gene, the first having no mutation, the second having a C357T mutation, and the third having both C357T and A385T mutations, which we designated as Se1, Se2, and sej, respectively. Among 226 Japanese individuals, 40 having a Le(a؉b؊) phenotype and 5 having a Le(a؊b؊) nonsecretor phenotype were homozygous for sej/sej, whereas 149 having a Le(a؊b؉) phenotype and 32 having a Le(a؊b؊)-secretor phenotype possessed at least one Se1 or Se2.The frequencies of occurrence of Se1, Se2, and sej among 410 alleles examined in a random sample of 205 Japanese individuals were 15, 46, and 39%, respectively, indicating a rather wide distribution of the sej allele in the Japanese population. The results show that the Sec2 gene really encodes the secretor enzyme ␣(1,2)fucosyltransferase and indicate that a ethnic group-specific nonsense or missense point mutation in the Sec2 gene determines nonsecretor status. The phylogenic aspect and biological significance of the Se and Le genes are discussed.
Angiotensin II (Ang II) up-regulates plasminogen-activator inhibitor type-1 (PAI-1) expression in mesangial cells to enhance extracellular matrix formation. The proximal promoter region (bp -87 to -45) of the human PAI-1 gene contains several potent binding sites for transcription factors [two phorbol-ester-response-element (TRE)-like sequences; D-box (-82 to -76) and P-box (-61 to 54), and one Sp1 binding site-like sequence, Sp1-box 1 (-72 to -67)]. We studied this region to determine the transcription factor(s) that mediates Ang-II-induced transcriptional activation of the PAI-1 gene. Various double-stranded decoy oligodeoxynucleotides (ODNs) corresponding to various sequences in the proximal promoter region were transfected to mesangial cells to examine the effects on Ang-II-induced PAI-1 mRNA expression. Transfection with the full-length decoy (bp -87 to -45, D-P-ODN) markedly attenuated Ang-II-induced PAI-1 mRNA expression by up to 70%. Transfection with D-ODN (-87 to -71) and P-ODN (-66 to -45), which correspond to each of the two TRE-like sequences, did not attenuate the expression. Gel-shift assays using nuclear extracts prepared from Ang-II-treated mesangial cells and D-P-ODN showed three specific complexes. The major complex was supershifted by anti-Sp1 antibody. The methylation-interference experiment demonstrated that human recombinant Sp1 bound to the so-called GT box (TGGGTGGGGCT, -78 to -69), which contains the Sp1-box 1. The complex that migrated with anti-Sp1 antibody was enhanced in the cells treated with Ang II. Further, D-Sp1-ODN (-85 to -63) containing the GT box attenuated up-regulation of PAI-1 mRNA expression induced by Ang II to a level (68±9% inhibition) comparable to D-P-ODN, whereas ODN with four mutations in the GT box had no effect. Our findings suggest that binding of Sp1 or an Sp1-like transcription factor to the GT box in the PAI-1 promoter up-regulates PAI-1 gene transcription in mesangial cells stimulated with Ang II. This transcription-factor binding site may be targeted to control Ang-II-dependent extracellular matrix formation by mesangial cells.
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