BIOL 200 Lecture 7: BIOL 200 Notes up to Midterm
25 Jan 2017
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The mrna is translationally dormant because maskin not only binds to eif4e but it binds to the same site on eif4e that would bind to another member of the eif4 family essential for active cap binding complex formation. Thus maskin blocks assembly of eif4 complex, thus blocking association of these messages with the ribosome. After egg fertilization, these mrnas are activated by cytoplasmic polyadenylation cpeb is phosphorylated and does not bind to maskin anymore. This allows cytoplasmic forms of cpsf and pap to bind, and allowing eif4e to associate with eif4g, and addition of a residues to mrna recruited to ribosome as eif4 complex is assembled. The au-rich element binding proteins recruit a deadenylating enzyme (to remove poly(a) tail) and the exosome to degrade these mrnas. Regulated degradation is a mechanism used to silence expression of certain genes: eg: regulation of ire-bp (iron response element binding protein)
