NUP98 fusion oncoproteins interact with the APC/C^Cdc20as a pseudosubstrate and prevent mitotic checkpoint complex binding

Abstract

NUP98 is a recurrent partner gene in translocations causing acute myeloid leukemias and myelodisplastic syndrome. The expression of NUP98 fusion oncoproteins has been shown to induce mitotic spindle defects and chromosome missegregation, which correlate with the capability of NUP98 fusions to cause mitotic checkpoint attenuation. We show that NUP98 oncoproteins physically interact with the APC/C Cdc20 in the absence of the NUP98 partner protein RAE1, and prevent the binding of the mitotic checkpoint complex to the APC/C Cdc20 . NUP98 oncoproteins require the GLEBS-like domain present in their NUP98 moiety to bind the APC/C Cdc20 . We found that NUP98 wild-type is a substrate of APC/C Cdc20 prior to mitotic entry, and that its binding to APC/C Cdc20 is controlled via phosphorylation of a PEST sequence located within its C-terminal portion. We identify S606, within the PEST sequence, as a key target site, whose phosphorylation modulates the capability of NUP98 to interact with APC/C Cdc20 . We finally provide evidence for an involvement of the peptidyl-prolyl isomerase PIN1 in modulating the possible conformational changes within NUP98 that lead to its dissociation from the APC/C Cdc20 during mitosis. Our results provide novel insight into the mechanisms underlying the aberrant capability of NUP98 oncoproteins to interact with APC/C Cdc20 and to interfere with its function.

The miR-196b miRNA inhibits the GATA6 intestinal transcription factor and is upregulated in colon cancer patients

“…Cell growth was assessed using the trypan blue dye exclusion staining and cell counting using a Burker chamber. Monovariate and bivariate cell cycle analyses were performed as described in [ 38 , 39 ]. Briefly, DNA content was measured by propidium iodide (50mg/ml) staining of and cytofluorimetry.…”

CDC20 in and out of mitosis: a prognostic factor and therapeutic target in hematological malignancies

“…APC/C CDC20 also showed an aberrant interaction with NUP98 fusion oncoproteins [ 148 ], a rare pathogenic mechanism in AML that is, however, overrepresented in high-risk pediatric patients [ 149 ]. Wildtype NUP98 is a conditional target of APC/C CDC20 and the physical interaction is dependent on the phosphorylation of a PEST sequence within NUP98 C-terminal domain, which occurs prior to mitotic entry [ 150 ]. The peptidyl-prolyl isomerase PIN1 then induces NUP98 conformational changes driving its dissociation from APC/C CDC20 during mitosis.…”

“…Conversely, Salsi et al demonstrated that NUP98 fusion oncoproteins bind APC/C CDC20 during mitosis, through the NUP98 GLEBS-like domain in the absence of the RAE1 partner protein. This interaction led to BUBR1 displacement and consequent attenuation of the SAC [ 148 ], that could be restored by CDC20 or MAD2 overexpression [ 150 ].…”

The balance between mitotic death and mitotic slippage in acute leukemia: a new therapeutic window?

“…1c). The expression of NUP98 fusions causes premature securin degradation in the presence of unsatisfied SAC, by interacting with APC/C Cdc20 and displacing BUBR1 [28, 29]. In parallel, degradation of cyclin B1 results in MPF complex inactivation and reversal of the CDK1 phosphorylation cascade by cellular phosphatases (e.g., PP1 and PP2A), which remove CDH1 inhibitory phosphorylation.…”