• Development and Reproduction
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• v.5 no.2
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• pp.131-136
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• 2001

The developmental profiles of rpr, grim, dcp-1, diapl, diap2 transcripts, which were involved in programmed cell death, were analyzed using competitive RT-PCR in whole animals during Drosophila development. The fluctuation patterns of transcript levels of the apoptotic initiators(rpr and grim) were similar to those of the ecdysone titer in Drosophila life cycle. The transcript of dcp-1, which is considered as effector caspase, was expressed strong1y at early embryo and female adult stages. However, the transcript levels of anti-apoptotic factors diap1 and diap2, showed the reverse pattern comparing with those of apoptotic factors(rpr and grim). Also, the transcript levels of rpr, diap2 and dcp-1 were quantified in the salivary glands and wing discs dissected from the wandering late third instar larva. The transcript levels of rpr and diap2 were changed reversely each other in both tissues from wandering stage to puparium formation. These results suggest that the expressions of cell death related genes are regulated by the ecdysone signals during normal development.

• Molecules and Cells
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• v.20 no.3
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• pp.446-451
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• 2005

Diap1 is an essential Drosophila cell death regulator that binds to caspases and inhibits their activity. Reaper, Grim and Hid each antagonize Diap1 by binding to its BIR domain, activating the caspases and eventually causing cell death. Reaper and Hid induce cell death in a Ring-dependent manner by stimulating Diap1 auto-ubiquitination and degradation. It was not clear that how Grim causes the ubiquitination and degradation of Diap1 in Grim-dependent cell death. We found that Grim stimulates poly-ubiquitination of Diap1 in the presence of UbcD1 and that it binds to UbcD1 in a GST pull-down assay, so presumably promoting Diap1 degradation. The possibility that dBruce is another E2 interacting with Diap1 was examined. The UBC domain of dBruce slightly stimulated poly-ubiquitination of Diap1 in Drosophila extracts but not in the reconstitution assay. However Grim did not stimulate Diap1 poly-ubiquitination in the presence of the UBC domain of dBruce. Taken together, these results suggest that Grim stimulates the poly-ubiquitination and presumably degradation of Diap1 in a novel way by binding to UbcD1 but not to the UBC domain of dBruce as an E2.

• Molecules and Cells
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• v.24 no.3
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• pp.445-451
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• 2007

Translation initiation factor 4E (eIF4E) is a key regulator of protein synthesis. Abnormal regulation of eIF4E is closely linked to oncogenic transformation. Several regulatory mechanisms affecting eIF4E are discussed, including transcriptional regulation, phosphorylation and binding of an inhibitor protein. However it is not clear how the level of eIF4E protein is regulated under basal conditions. Here we demonstrate that Diap1 (Drosophila Inhibitor of Apoptosis Protein), a cell death inhibitor, binds directly to eIF4E and poly-ubiquitinates it via its E3 ligase activity, promoting its proteasome-dependent degradation. Expression of Diap1 caused a reduction of Cyclin D1 protein level and inhibited the growth stimulation induced by overexpression of eIF4E. Taken together, our results suggest that the level of eIF4E protein is regulated by Diap1, and that IAPs may play a role in cap-dependent translation by regulating the level of eIF4E protein.