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.

t. As with the discovery of P bodies, our observations suggest that the intracellular distributions of key proteins involved in the control of translation and mRNA degradation represent a significant factor in these proteins' functionalities. This proposed mode of action is also in accord with the earlier observation that Dhh1, Pat1 and Lsm1-7 are involved in the transition of brome mosaic virus from translation to replication (36) . Indeed, helicases are likely to be involved in such transitions in a wide range of positive-strand RNA viruses (including HCV and severe acute respiratory syndrome coronavirus) (37, 38) . In this context, it is also interesting to note the earlier observation that deletion of PAT1 in S. cerevisiae suppresses the deleterious effects of PAB1 deletion (5), since this may again be attributable to effects on mRNP structure associated with the presence of Pat1. Finally, the segregation phenomenon described here provides a potential explanation why Dhh1 and Pat1 do not inhibit protein synthesis in vivo during exponential growth yet act as inhibitors when added to cell-free extracts (4) .