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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 [alpha] (PML/RAR[alpha]) 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/RAR[alpha]-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/RAR[alpha] interaction and promoter transactivation. However, EMSA results showed that PML/RAR[alpha] 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/RAR[alpha]a regulation. This study shows that PML/ RAR[alpha] 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. transcription | regulation | GAGC motif | acute promyelocytic leukemia | coagulopathy doi/10.1073/pnas.0915006107

Biochemical and genetic analyses were conducted on the platelet proteins of a patient suffering from a variant of Glanzmann thrombasthenia. This disease is characterized by the absence of platelet aggregation due to a defect in the integrin alpha-IIb-beta-3. The results showed that the functional defect in this integrin is due to a Ser-752 to Pro mutation in the cytoplasmic domain of beta-3. This results in a coupling failure between cellular activation and up-regulation of the integrin for fibrinogen.

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. [ABSTRACT FROM AUTHOR]