Fig. 2.

Ubiquitylome analysis of the aging proteome in fly heads. a Proportions of ¹⁵N-PSMs in total PSMs. While ¹⁵N-labeled old forms accounted for 28% of the entire proteome at 60d, they represented 59% of the ubiquitylated proteome, suggesting increased ubiquitylation in older proteome. b Quantifications of ¹⁵N signals in total proteins and ubiquitylated proteins. A scatter plot of ¹⁵N ratio confirms a majority of the proteins have higher ¹⁵N proportion in ubiquitylome than that of the normal aging proteome at 60d of age (p = 2.2e-16, Mann–Whitney-Wilcoxon test). c, d Ubiquitylated histone proteins are featured by higher ¹⁵N ratios, including H2A (c) and H2B (d). The XICs of the paired ¹⁵N and ¹⁴N peaks were compared. e Quantification of ¹⁵N proportions and abundance of ubiquitylated sites. H2A has high-abundance in the level of ubiquitylation, as assessed by the PSM counts