Ubiquitin-like protein 5 is a protein that in humans is encoded by the UBL5gene.
It has been shown that in C. elegans mitochondria treated to lower expression of certain electron transport chain proteins during the L3/L4 stage, its expression levels is higher leading to increased lifespans. 
Ubiquitin-like proteins (UBLs) are thought to be reversible modulators of protein function rather than protein degraders like ubiquitin (MIM 191339).[supplied by OMIM]
Friedman JS, Koop BF, Raymond V, Walter MA (2001). "Isolation of a ubiquitin-like (UBL5) gene from a screen identifying highly expressed and conserved iris genes". Genomics71 (2): 252–5. doi:10.1006/geno.2000.6439. PMID11161819.
Wilkinson CR, Dittmar GA, Ohi MD, et al. (2005). "Ubiquitin-like protein Hub1 is required for pre-mRNA splicing and localization of an essential splicing factor in fission yeast". Curr. Biol.14 (24): 2283–8. doi:10.1016/j.cub.2004.11.058. PMID15620657.
Rual JF, Venkatesan K, Hao T, et al. (2005). "Towards a proteome-scale map of the human protein-protein interaction network". Nature437 (7062): 1173–8. doi:10.1038/nature04209. PMID16189514.