Differential effects of Wilms tumor WT1 splice variants on the insulin receptor promoter.
The Wilms tumor gene WT1 has been implicated in the early development of the kidney. Mutations in WT1 are found in a small fraction of Wilms tumor, a pediatric nephroblastoma, and Denys-Drash syndrome, characterized by genitourinary abnormalities. The WT1 gene product functions as a transcriptional repressor of growth factor-related genes. The kidney is one of the major sites of insulin action in vivo and expresses high levels of insulin receptors (IR). IR expression has been detected during early embryogenesis, suggesting that it may play a role in development. We investigated whether two WT1 splice variants lacking or including a three-amino-acid (KTS) insertion between the third and fourth zinc finger in the DNA-binding domain could repress the IR promoter in vitro. We show that the +KTS variant effectively represses promoter activity under all conditions tested but the -KTS variant was only able to repress in the presence of cotransfected C/EBP beta or a dominant-negative p53 mutation. Deletional mapping indicated that distinct regions of the IR promoter mediated the effects of the two isoforms and DNaseI footprint analysis identified potential WT1 binding sites within these regions.
Webster
N J
NJ
UCSD/Whittier Diabetes Program, University of California, San Diego, La Jolla 92093, USA. nwebster@ucsd.edu
Kong
Y
Y
Sharma
P
P
Haas
M
M
Sukumar
S
S
Seely
B L
BL
D017398:Alternative Splicing / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D006528:Carcinoma, Hepatocellular; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D016162:Genes, Wilms Tumor / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D051381:Rats; D011972:Receptor, Insulin / Q000235:genetics*; D017384:Sequence Deletion; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D025721:WT1 Proteins; D009396:Wilms Tumor / Q000235:genetics; D016335:Zinc Fingers / Q000235:genetics
D004268:DNA-Binding Proteins; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D025721:WT1 Proteins; D011972:Receptor, Insulin