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 parentheses; decay curves for 40 randomly selected mRNAs, excluding five outliers (see Fig. *D*), encoding unique ribo some subunits are shown. (*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 parentheses. Red open circles, half-lives of individual mRNAs within each complex; thick black bar, the mean half-life for each complex; 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* ≥ 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 (10^{4} times) of *N* samples from 4,482 unique mRNA half-lives was then determined and summarized in the histogram. 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—*RPS4A*, *RPS4B*, *RPL3*, *RPS27A*, and *RPS28B* (average of triplicate measurements)—with very short half-lives (*t*_{1/2} < 10 min).

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