Recent advances in defining the ubiquitylome

Ubiquitin is a small 8.5 kDa protein that is conjugated to a target protein in a concerted three step enzymatic process. Ubiquitin addition can drastically affect function or target the modified protein for degradation. Ubiquitin modifications have important regulatory roles in disease progression, such as in cancer and neurodegenerative diseases to name a few. As a consequence, it is imperative to identify important ubiquitin targets to elucidate the role of the modification. Proteomic studies have sought to understand this role by identifying proteome-wide ubiquitylated proteins. Two central ideas have developed to characterize the ubiquitylome: affinity purification of ubiquitylated proteins and optimization of GG-peptide enrichment. In this review, we will discuss recent advances in both approaches and discuss how these studies are essential to pharmacoproteomics.