ABSTRACT
We have used the human H blood group alpha(1,2)fucosyltransferase (FUT1) cDNA to screen chromosome 19 cosmid libraries in a search for the human Secretor (Se) blood group gene (FUT2). One cosmid has been isolated that contains two distinct segments that cross-hybridize with FUT1. We have assembled a 100-kilobase (kb) cosmid contig, localized to 19q13.3, encompassing FUT1 and the two FUT1-related sequences, termed Sec1 and Sec2, for Secretor candidate 1 and 2. Sec1 and Sec2 are separated by 12 kb and are 65.5 kb and 35 kb apart, respectively, from the FUT1 gene. We used a cosmid-dependent direct cDNA selection method to clone a cDNA corresponding to a transcript that emanates from Sec2. This cDNA detects a 3.35-kb transcript in human tissues known to express the Se locus. Together with sequence and expression data reported in the accompanying article (Kelly, R. J., Rouquier, S., Giorgi, D., Lennon, G. G., and Lowe, J. B. (1995) J. Biol. Chem. 270, 4640-4649), these data demonstrate that Sec2 corresponds to the human Se blood group locus (FUT2). Our results furthermore define the physical relationship between the H and Se loci and confirm a hypothesis that these two loci represent distinct but closely linked alpha(1,2)fucosyltransferase genes.
Subject(s)
Blood Group Antigens/genetics , Fucosyltransferases/genetics , Animals , Chromosomes, Artificial, Yeast , Chromosomes, Human, Pair 19 , Cloning, Molecular , Cosmids , Cricetinae , Cricetulus , DNA, Complementary/genetics , Deoxyribonuclease EcoRI , Genome, Human , Humans , Hybrid Cells , In Situ Hybridization, Fluorescence , Intestinal Mucosa/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Restriction Mapping , Galactoside 2-alpha-L-fucosyltransferaseABSTRACT
DNA from a 50-kb yeast artificial chromosome (YAC) containing one human telomere was characterized. Cloned sequences from the centromeric end of this YAC (designated yRM2001) localized to several human chromosomes by somatic hybrid panel mapping. The telomeric end of the YAC contained both (TTAGGG)n sequences and the previously characterized TelBam3.4 subterminal repeat element. A novel low-copy repeat element (designated HC1103) mapped 19 kb from the telomeric end of the YAC. This repeat was shown by fluorescence in situ hybridization to be present in several subtelomeric regions (3q, 12p, 15q, 19p, and 20p) and at an interstitial site (2q13-->q14) in all individuals studied, but to be polymorphically distributed at several other telomeres. The YAC vector-insert EcoRI cloning site was positioned 50 kb to 70 kb from chromosome termini in human genomic DNA using RecA-assisted restriction endonuclease (RARE) cleavage analysis. Our results suggest that the DNA segment cloned in yRM2001 contains a novel block of low-copy DNA consistently present at some human telomeres, but polymorphically distributed at others.
