Characterization of bidirectional promoter of mouse endonuclease III (Nthl1) and tuberous sclerosis 2 (Tsc2) genes

Ikeda S, Mochizuki, A., Seki Y, and Ayabe, H..

The gene for the mammalian endonuclease III homolog (Nthl1) lies immediately adjacent to the Tsc2 gene, a tuberous sclerosis disease-determining gene, in a head-to-head orientation.  Using a luciferase assay, we previously identified a short spacer sequence between the mouse Nthl1 and Tsc2 genes that is essential for bidirectional transcription, and demonstrated that the expression of both of these 2 genes is regulated by a core promoter that contains Ets-transcription factor binding site.  In the present study, we further characterized the Nthl1/Tsc2 promoter, and detected a novel functional element, probably a Tst-1 binding site, that only exhibits positive regulation of Tsc2 transcription.  Overexpression of the Ets-family proteins c-Ets1 and p55-erg negatively affected the activity of the bidirectional promoter, suggesting that these Ets-family proteins are not responsible for the transcription of Nthl or Tsc2.  The promoter's activities in the Nthl1 and Tsc2 directions were simultaneously measured in various cell lines using a plasmid that contains the core promoter sequence and 2 different reporter genes (one on each side of the promoter).  The results show that the activity ratio of Tsc2- to Nthl1-transcription varies among the different cell types, indicating that transcription in each direction (Tsc2 and Nthl1) is regulated in a separate manner.

The Bulletin of Okayama University of Science

37A

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