Fig. 1.

Selective degradation of long-lived proteins mitigates their accumulation in quiescent cells. (A) Schematic outlines the relationship between [protein], k_synthesis, k_degradation, and k_division in dividing and quiescent cells. (B) The measured distribution of k_degradation in dividing cells indicating the percentage of the proteome with k_degradation values greater or less than k_division. These two classes of proteins are referred to as “short-lived” and “long-lived,” and their clearance is dominated by degradation and cell division, respectively. (C) Relationship between relative protein expression levels in quiescent and dividing cells to k_degradation in dividing cells. Box plots indicate the distribution of log₂ [protein] ratios within different ranges of k_degradation in dividing cells. The box indicates the interquartile range (IQR), and the line indicates the median. Far outliers (>1.5*IQR) were excluded. The color scale refers to distribution shown in B. The orange line indicates the theoretical relationship between log₂ [protein] ratios and k_degradation in the absence of changes in k_degradation and k_synthesis between dividing and quiescent cells (see kinetic model). (D) Relationship between relative protein synthesis rates in quiescent and dividing cells to k_degradation in dividing cells. (E) Relationship between relative protein degradation rates in quiescent and dividing cells to k_degradation in dividing cells. (F) Box plots indicate the distribution of log₂ ratio of k_degradation measurements between quiescent and dividing cells for proteins mapped to different gene ontology (GO) component accessions.