Participation of Leaky Ribosome Scanning in Protein Dual Targeting by Alternative Translation Initiation in Higher Plants

Authors

Yashitola Wamboldt, University of Nebraska - Lincoln
Saleem Mohammed, University of Nebraska - Lincoln
Christian Elowsky, University of Nebraska-LincolnFollow
Chris Wittgren, University of Nebraska - Lincoln
Wilson B. M. de Paula, University of Nebraska - Lincoln
Sally Ann MacKenzie, University of Nebraska-LincolnFollow

ORCID IDs

Christian Elowsky

Date of this Version

1-2009

Citation

The Plant Cell, Vol. 21: January 2009, pp. 157–167.

Comments

Copyright 2009 American Society of Plant Biologists. Used by permission.

Abstract

Postendosymbiotic evolution has given rise to proteins that are multiply targeted within the cell. Various mechanisms have been identified to permit the expression of proteins encoding distinct N termini from a single gene. One mechanism involves alternative translation initiation (aTI). We previously showed evidence of aTI activity within the Arabidopsis thaliana organellar DNA polymerase gene POLg2. Translation initiates at four distinct sites within this gene, two non-AUG, to produce distinct plastid and mitochondrially targeted forms of the protein. To understand the regulation of aTI in higher plants, we used Polg2 as a model to investigate both cis- and trans-acting features of the process. Here, we show that aTI in Polg2 and other plant genes involves ribosome scanning dependent on sequence context at the multiple initiation sites to condition specific binding of at least one trans-acting factor essential for site recognition. Multiple active translation initiation sites appear to operate in several plant genes, often to expand protein targeting. In plants, where the mitochondrion and plastid must share a considerable portion of their proteomes and coordinate their functions, leaky ribosome scanning behavior provides adaptive advantage in the evolution of protein dual targeting and translational regulation.