Figure 7
From: Expression and Regulation of Deubiquitinase-Resistant, Unanchored Ubiquitin Chains in Drosophila
Model of unanchored poly-Ub regulation in vivo. Unanchored poly-Ub can be dismantled into mono-Ub and reutilized in future Ub reactions by the coordinated action of E1/E2/E3. This is the canonical model of Ub recycling. Our results in Drosophila suggest the possibility of other, non-mutually exclusive mechanisms of unanchored Ub chain control: their degradation as whole units by the proteasome; their reutilization en bloc, enabling the conjugation of the entire chain onto a substrate without the prior need for dismantling into mono-Ub; or their maintenance in a separate, “reserve” pool through interaction with Ub-binding proteins. The “reserve” pool could feed into the other routes.
