Figure 3: mRNA encoding the subunits of stoichiometric protein complexes exhibit coordinated decay. (A) Examples of coordinated decay of transcripts for four stoichiometric protein complexes. The number of unique components in each complex is indicated in brackets; 40 randomly selected mRNAs encoding unique ribosome subunits were presented. (B) Clustering of the decay half-lives of mRNAs encoding subunits of protein complexes. The number of unique components in each complex is indicated in brackets. Red open circles, half-lives of individual mRNAs within each complex; thick black bar, the mean half-life for each complex; the error bars, indicate ± 1 SD. The complexes are sorted along the vertical axis (top to bottom) in the order of increasing mean half-lives. (C) Statistical test for the coordinated decay of subunits of stoichiometric protein complexes with N ³ 2 components. A p-value for the clustering of decay rates of transcripts for each physical complex of size of N was calculated. The probability of obtaining a smaller p-value from random sampling (104 times) of N samples from 4482 unique mRNA half-lives was then determined and summarized in the histrogram. The dashed line represents the uniform distribution expected for the null hypothesis in which there is no coordination of decay rates.

(D) A small set of mRNAs encoding ribosomal proteins has anomalously fast decay rates. Blue curve, average decay curve of 131 RP mRNAs; error bars, indicate ± 1 SD; green curves, decay curves of five individual mRNAs (average of triplicate measurements) with very short half-lives (t1/2 < 10 min), RPS4A, RPS4B, RPL3, RPS27A, and RPS28B.