Evolution of the tandem repeats in thymidylate synthase enhancer region (TSER) in primates.
The upstream regulatory region of the human thymidylate synthase gene (thymidylate synthase enhancer region, TSER) is length polymorphic, attributable to variable numbers of tandemly repeated copies of a 28-bp fragment. It has been found that TSER length polymorphism is correlated to malignancy risk. To further our understanding of the origin and evolution of TSER, this region was investigated among different primates, including hominoids, two subfamilies of the Old World monkeys (OWMs): colobines and cercopithecines, and two species of the New World monkeys (NWMs). In addition to humans, our results show that length polymorphism in TSER is also present in some primate populations, although it appears that this region is length monomorphic in many other primates. We identified three unique repeat motifs in TSER and defined them as R1, R2, and R3, respectively, starting from the 3' end. The same repeat motifs from different species are more similar to each other than different repeat motifs within same species are. Such a paraphyletic pattern suggests that divergence of the three repeat motifs predated divergence of the OWMs/hominoids and the NWMs. The most recent common ancestor (MRCA) of hominoids and the OWMs probably possessed triple repeats but now double and triple repeats are two dominant types in hominoids and the OWMs. In addition, our results show that each of the three repeat motifs may be lost independently. We have also found clues that recombination was involved in formation of tandem repeat polymorphism in TSER.
Laboratory of Cellular and Molecular Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, PR China.
Yun-Wu
YW
Zhang
Huai-Rong
HR
Luo
Oliver A
OA
Ryder
Ya-Ping
YP
Zhang
D000483:Alleles; D000818:Animals; D001483:Base Sequence; D002520:Cercopithecidae / Q000235:genetics; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D019143:Evolution, Molecular; D005787:Gene Frequency; D014644:Genetic Variation; D006801:Humans; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D011323:Primates / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D020080:Tandem Repeat Sequences / Q000235:genetics*; D013940:Thymidylate Synthase / Q000235:genetics*
D004247:DNA; D013940:Thymidylate Synthase