Diauxic shift-dependent relocalization of decapping activators Dhh1 and Pat1 to polysomal complexes

Drummond, Sheona P.; Hildyard, John; Firczuk, Helena; Reamtong, Onrapak; Li, Ning; Kannambath, Shichina; Claydon, Amy J.; Beynon, Robert J.; Eyers, Claire E.; McCarthy, John E. G.

In contrast to these other reported subcellular systems, in this article, we have described a form of molecular segregation that may not involve the formation of a specific type of coherent intracellular body, but does involve the accumulation of proteins that are effectively excluded from actively translating polysomal mRNPs. This phenomenon is also distinct in that it occurs during exponential growth, and appears to be a form of spatial modulation of the function(s) of Dhh1 and Pat1, both of which are thought to promote mRNA decapping as well as inhibit translation. We have also shown that the degree of co-localization of Dhh1 and Pat1 with Figure S4) . Comparison of the polysomal distributions of the respective proteins and the quantitation data (Figures 2 and 3) indicates that, during exponential growth, a substantial part of the Dhh1 and Pat1 co-localizes with translation factor pools that cycle on and off mRNP complexes. Subsequent to the diauxic growth shift, on the other hand, Dhh1 and Pat1 co-localize to an increased degree with translation factors that are engaged with actively translating polysomal mRNP. Since the intracellular abundance of the translation factors and mRNA has yet to be determined in ethanol respiration phase cells, we interpret the absolute co-localization percentages only as a relative guide to the overall shift in association between the respective components under study.