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XB-ART-4430
Mol Cell Biol 2003 Dec 01;2323:8795-808. doi: 10.1128/MCB.23.23.8795-8808.2003.
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Retinoic acid receptor alpha fusion to PML affects its transcriptional and chromatin-remodeling properties.

Segalla S , Rinaldi L , Kilstrup-Nielsen C , Badaracco G , Minucci S , Pelicci PG , Landsberger N .


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PML-RAR is an oncogenic transcription factor forming in acute promyelocytic leukemias (APL) because of a chromosomal translocation. Without its ligand, retinoic acid (RA), PML-RAR functions as a constitutive transcriptional repressor, abnormally associating with the corepressor-histone deacetylase complex and blocking hematopoietic differentiation. In the presence of pharmacological concentrations of RA, PML-RAR activates transcription and stimulates differentiation. Even though it has been suggested that chromatin alteration is important for APL onset, the PML-RAR effect on chromatin of target promoters has not been investigated. Taking advantage of the Xenopus oocyte system, we compared the wild-type transcription factor RARalpha with PML-RAR as both transcriptional regulators and chromatin structure modifiers. Without RA, we found that PML-RAR is a more potent transcriptional repressor that does not require the cofactor RXR and produces a closed chromatin configuration. Surprisingly, repression by PML-RAR occurs through a further pathway that is independent of nucleosome deposition and histone deacetylation. In the presence of RA, PML-RAR is a less efficient transcriptional activator that is unable to modify the DNA nucleoprotein structure. We propose that PML-RAR, aside from its ability to recruit aberrant quantities of histone deacetylase complexes, has acquired additional repressive mechanisms and lost important activating functions; the comprehension of these mechanisms might reveal novel targets for antileukemic intervention.

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Species referenced: Xenopus
Genes referenced: rab40b

References [+] :
Belikov, Hormone activation induces nucleosome positioning in vivo. 2000, Pubmed, Xenbase