Functional analysis of PML protein in the ubiquitin system

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PML protein has a typical RING finger domain and there is in the nuclei-inclusion body known as POD. A RING ringer motif is found in typical ubiquitin ligase (E3). The translocation on PML and retinoic acid-receptor alpha (RARα) gene working as a transcription iactor is occurred in APL patients. The chemical therapy with retinoic acid-inoculation resulted, somehow, in reconstitution of POD and degradation of PML-RARa fusion protein depending on ubiquitin-proteasome pathway. However the molecular mechanism of PML-RARα protein degradation has not been clear.We investigated the relationships between a ubiquity conjugation enzyme (E2) and PML protein, therefore, imrnunoprecipitation and western blotting analysis were carried out after transfection with PML and each E2 gene. As a result, only UbcH9 could be detected to bind PML protein for SUMOylation. It takes it for granted because PML is typical targeted for SUMOylation and the system is required for UbcH9 as E2 protein. PML, PML-RARα, and E2 genes were transfected into HEK293 cells and analyzed on protein stability on PML and PML-RARα proteins. The stability of the proteins was pretty well in the presence of retinoic acid The PML protein was hyper SUMOylated in the presence of retinoic acid and pory-SUMOylated. It does not seem that PML protein has E3 ligase activity in spite of typical RING finger motif. The investigation will be required to the role for SUMOylation in the pathogenesis of APL.