Ubp3 & Rsp5
- ubiquitin protease Ubp3 and its cofactor Bre5 are required for ribophagy, however not for bulk autophagy
- a catalytically inactive mutant of Ubp3 also displayed a defect in ribophagy -> regulation takes place by ubiquitinylation
- Ubp3 cleaves ubiquitin fusions but not polyubiquitin
- Rsp5 is an ubiquitin ligase, involved in regulating many cellular processes including MVB sorting, heat shock response, transcription, endocytosis, and ribosome stability
Whi2 as a multicopy suppressor of a temperature sensitive mutant of RSP5, which is involved in ribophagy together with Ubp3. If we assume, that a defect in ribophagy, as an essential homeostasis pathway, is responsible for lethality of delta rsp5 mutants, the rescued could be explained by Whi2 multicopy-induced increased STRE gene expression and subsequent overexpression of bulk autophagy or other ribophagy associated proteins. A likely protein candidate in this context would be Ubp3, as it is also involved in ribophagy, cooperatively with Rsp5 controlling the ubiquitinylation state of ribosomes. To test this hypothesis, it could be looked up, whether Ubp3 contains a STRE promotor.