Functional studies of the deubiquitinating enzymes USP19, USP4 and UCH-L1
Velasco Pinto, Kelly Marcela
The conjugation of ubiquitin to proteins, known as ubiquitination, has different cellular functions; they include targeting proteins for degradation by the proteasome, regulation of DNA damage repair signaling, membrane receptor signaling and endocytosis (1). The ubiquitin moieties can be de-conjugated from their substrates or other ubiquitin moieties by a large group of proteases named deubiquitinating enzymes (DUBs) (2). DUBs are essential for the maintenance of the ubiquitin homeostasis in the cell and regulation of the ubiquitination status of the different substrates. The diversity of these proteases hints on their specificity for certain targets and participation in particular cellular pathways. Although several DUBs have been thoroughly studied, at present the targets and physiological roles of most of them remain unknown. Here, we studied the functional roles of the ubiquitin specific protease 19 (USP19), USP4 and the ubiquitin C-terminal hydrolase (UCH-L1), using several cellular and molecular techniques. We found that, i) USP19 can be regulated by SIAH ubiquitin ligases, ii) USP19 is important for controlling the key regulator of response to hypoxia, HIF-1α, iii) USP4 is a proteasome-interacting DUB, iv) an mCherry-UCH-L1 chimera reproduces only partially previous phenotypes described for UCH-L1, and v) UCH-L1 promotes Yersinia pseudotuberculosis internalization.