Structure, polymorphism, and novel repeated DNA elements revealed by a complete sequence of the human. cap alpha. -fetoprotein gene
The human ..cap alpha..-fetoprotein gene spans 19,489 base pairs from the putative Cap site to the polyadenylation site. It is composed of 15 exons separated by 14 introns, which are symmetrically placed within the three domains of ..cap alpha..-fetoprotein. In the 5' region, a putative TATAAA box is at position -21, and a variant sequence, CCAAC, of the common CAT box is at -65. There are six polymorphic sites within 4690 base pairs of contiguous DNA derived from two allelic ..cap alpha..-fetoprotein genes. This amounts to a measured polymorphic frequency of 0.13%, or 6.4 x 10/sup -4//site, which is about 5-10 times lower than values estimated from studies on polymorphic restriction sites in other regions of the human genome. There are four types of repetitive sequence elements in the introns and flanking regions of the human ..cap alpha..-fetoprotein gene. At least one of these is apparently a novel structure (designated Xba) and is found as a pair of direct repeats, with one copy in intron 7 and the other in intron 8. It is conceivable that within the last 2 million years the copy in intron 8 gave rise to the repeat in intron 7. Their present location on both sides of exon 8 gives these sequences a potential for disrupting the functional integrity of the gene in the event of an unequal crossover between them. There are three Alu elements, one of which is in intron 4; the others are located in the 3' flanking region. A solitary Kpn repeat is found in intron 3. Neither X, Xba, nor Kpn elements are present in the related human albumin gene, whereas Alu's are present in different positions. From phylogenetic evidence, it appears that Alu elements were inserted into the ..cap alpha..-fetoprotein gene at some time postdating the mammalian radiation 85 million years ago.
- Research Organization:
- Univ. of California, Riverside
- OSTI ID:
- 6411346
- Journal Information:
- Biochemistry; (United States), Vol. 26:5
- Country of Publication:
- United States
- Language:
- English
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