Figure 1. Cotranslational assembly of the Tea2p-Tip1p complex.

(A) RIp-chip experiments with Tea2p. The y axis shows the log₁₀ enrichment ratios in Tea2p RIp-chip experiments, standardised to make the mean and standard deviation equal to 0 and 1, respectively. The box plots show the distribution of enrichments, with the box showing the lower and upper quartiles, the whiskers representing data within the upper/lower quartile plus/minus 1.5-fold the interquartile range, and other data points displayed as circles. White circles represent mRNAs not considered significant (either because they are common contaminants in multiple RIp-chip experiments, or because they were not reproducibly enriched in independent replicas of the experiment), black circles correspond to mRNAs encoding the bait, and grey circles are used for mRNAs specifically associated with the bait protein. Left: Tea2p copurifies with wild type tip1 (+ATG), but not with tip1 that cannot be translated (−ATG). Right: The interaction between Tea2p and the tip1 and tea2 mRNAs is lost upon treatment of the cells with puromycin. (B) Three models to explain the association between Tea2p and the tip1 mRNA (see text for details). (C) Design of the −ATG experiment coupled to RIp-chip analysis. A single nucleotide mutation to the start codon prevents the translation of tip1. If the association between Tea2p and tip1 is cotranslational, lack of Tip1p should abolish their interaction.