Developmental timing of mRNA translation--integration of distinct regulatory elements

Targeted mRNA translation is emerging as a critical mechanism to control gene expression during developmental processes. Exciting new findings have revealed a critical role for regulatory elements within the mRNA untranslated regions to direct the timing of mRNA translation. Regulatory elements can be targeted by sequence-specific binding proteins to direct either repression or activation of mRNA translation in response to developmental signals. As new regulatory elements continue to be identified it has become clear that targeted mRNAs can contain multiple regulatory elements, directing apparently contradictory translational patterns. How is this complex regulatory input integrated? In this review, we focus on a new challenge area-how sequence-specific RNA binding proteins respond to developmental signals and functionally integrate to regulate the extent and timing of target mRNA translation. We discuss current understanding with a particular emphasis on the control of cell cycle progression that is mediated through a complex interplay of distinct mRNA regulatory elements during Xenopus oocyte maturation.