PML/RARα fusion protein transactivates the tissue factor promoter through a GAGC-containing element without direct DNA association
2010
Yan, Jinsong | Wang, Kankan | Dong, Leiming | Liu, Hongchen | Chen, Weiqin | Xi, Wenda | Ding, Qiulan | Kieffer, Nelly | Caen, Jacques P. | Chen, Saijuan | Chen, Zhu | Xi, Xiaodong
A severe coagulopathy is a life-threatening complication of acute promyelocytic leukemia (APL) and is ascribable mainly to the excessive levels of tissue factor (TF) in APL cells regulated in response to the promyelocytic leukemia/retinoic acid receptor α (PML/RARα) fusion protein. The underlying molecular mechanisms for this regulation remain ill-defined. With U937-PR9 cell lines stably expressing luciferase reporter gene under the control of different mutants of the TF promoter, both luciferase and ChIP data allowed the localization of the PML/RARα-responsive sequence in a previously undefined region of the TF promoter at position -230 to -242 devoid of known mammalian transcription factor binding sites. Within this sequence a GAGC motif (-235 to -238) was shown to be crucial because deletion or mutation of these nucleotides impaired both PML/RARα interaction and promoter transactivation. However, EMSA results showed that PML/RARα did not bind to DNA probes encompassing the -230 to -242 sequences, precluding a direct DNA association. Mutational experiments further suggest that the activator protein 1 (AP-1) sites of the TF promoter are dispensable for PML/RARα regulation. This study shows that PML/RARα transactivates the TF promoter through an indirect interaction with an element composed of a GAGC motif and the flanking nucleotides, independent of AP-1 binding.
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