Joyce’s Weblog

Hacer investigacion es toda una experiencia que todos deberian experimentar. Es enfrentarse a diferentes problemas y resolverlos de la mejor manera posible. En el camino se encuentran muchas dificultades pero es gratificante poder sobrepasarlas…

An Interaction between Mex67p and Upf1p at the Terminal Step

of mRNA Export Facilitates mRNA Translation

Abby J. Agosto, Iván J. Cajigas, Paloma M. Guzzardo, Heike Krebber and

Carlos I. González

Gene expression relies on the communication between the processes of transcription, mRNA processing, export and translation. Once synthesized in the nucleus, an mRNA must become competent for its translocation across the nuclear pore. Formation of an mRNA particle (mRNP) suitable for export is accomplished by the binding of soluble export factors to the nascent mRNA. Following transport, mRNPs must undergo structural rearrangements in the cytoplasm in order to enter translation. We have gathered information to support this mRNP remodeling step. Specifically, we have found that Mex67p interacts with Upf1p. We provide evidence to support the notion that the Mex67p-Upf1p interaction is neither required for the activation of the NMD pathway or for poly-(A)+ mRNA export. Instead, Upf1p and Mex67p are critical to facilitate the conversion from an export-competent mRNP to a translation-competent mRNP, since cells lacking both proteins demonstrate severe defects in protein synthesis. Specifically, our data demonstrate that these cells are unable to efficiently initiate mRNA translation and recognize translation termination codons. We propose that in the cytoplasm, Upf1p communicates the Mex67p-bound mRNAs with the protein synthesis machinery to facilitate translational competency and couple the terminal step of mRNA export to mRNA translation.