tailieunhanh - Báo cáo khoa học: The HNF1b transcription factor has several domains involved in nephrogenesis and partially rescues Pax8/lim1-induced kidney malformations

The tissue-specific transcription factorsHNF1aandHNF1b are closely related homeodomain proteins conserved in vertebrate evolution. Heterozygous mutations in human HNF1b 1 but not inHNF1agenes are associated with kidney malformations. Overexpression of HNF1b in Xenopus embryos leads to defective pronephros development, while HNF1ahas no effect. We have defined the regions respon-sible for this functional difference between HNF1band HNF1ain transfected HeLa cells as well as in injected Xenopusembryos. . | Eur. J. Biochem. 271 3715-3728 2004 FEBS 2004 doi The HNF1P transcription factor has several domains involved in nephrogenesis and partially rescues Pax8 lim1-induced kidney malformations Guizhi Wu Silvia Bohn and Gerhart U. Ryffel Institut fur Zellbiologie Universitatsklinikum Essen Germany The tissue-specific transcription factors HNF1 a and HNF1 b are closely related homeodomain proteins conserved in vertebrate evolution. Heterozygous mutations in human HNF1b but not in HNF1a genes are associated with kidney malformations. Overexpression of HNF1b in Xenopus embryos leads to defective pronephros development while HNF1a has no effect. We have defined the regions responsible for this functional difference between HNF1b and HNF1a in transfected HeLa cells as well as in injected Xenopus embryos. Using domain swapping experiments we located a nuclear localization signal in the POUH domain of HNF1 b and showed that the POUS and POUH domains of HNF1b mediate a high transactivation potential in transfected cells. In injected Xenopus embryos three HNF1b domains are involved in nephrogenesis. These include the dimerization domain the 26 amino acid segment specific for splice variant A as well as the POUH domain. As HNF1b together with Pax8 and lim1 constitute the earliest regulators in the pronephric anlage it is possible that they cooperate during early nephrogenesis. We have shown here that HNF1b can overcome the enlargement and the induction of an ectopic pronephros mediated by overexpression of Pax8 and lim1. However the phenotype induced by Pax8 and lim1 overexpression and characterized by cyst-like structures and thickening of the pronephric tubules was not altered by HNF1b overexpression. Taken together HNF1b acts antagonistically to Pax8 and lim1 in only some processes during nephrogenesis and a simple antagonistic relationship does not completely describe the functions of these genes. We conclude that HNF1b has some distinct .