Local regulation of mRNA translation: new insights from the bud.

Active mRNA transport and localization is an efficient way for cells to regulate the site and time of expression of specific proteins. Recent publications have identified factors involved in the sorting and translational regulation of bud-localized transcripts in Saccharomyces cerevisiae and uncovered interplay between mRNA trafficking, translational regulation and ER inheritance. mRNA localization at the bud tip of yeast cells depends on the She2p-She3p-Myo4p complex. To avoid any ectopic expression, translation of the bud-localized ASH1 mRNA is repressed by the translational repressors Puf6p and Khd1p during its transport. As this complex reaches the bud tip, phosphorylation of Khd1p by the membrane-associated kinase Yck1p activates the local translation of this transcript, thereby defining a fine-tuning mechanism of Ash1p expression.