Plant 4/1 protein: potential player in intracellular, cell-to-cell and long-distance signaling

Sergey Y Morozov,Tatyana N Erokhina,Robert A Owens,Lilya Kopertekh,Andrey G Solovyev,Svetlana S Makarova,Joachim Schiemann

doi:10.3389/fpls.2014.00026

Abstract

Originally isolated as a result of its ability to interact with the movement protein of Tomato spotted wilt virus in a yeast two-hybrid system, the 4/1 protein is proving to be an excellent tool for studying intracellular protein trafficking and intercellular communication. Expression of 4/1 in vivo is tightly regulated, first appearing in the veins of the cotyledon and later in the vasculature of the leaf and stem in association with the xylem parenchyma and phloem parenchyma. Structural studies indicate that 4/1 proteins contain as many as five coiled–coil (CC) domains; indeed, the highest level of sequence identity among 4/1 proteins involves their C-terminal CC domains, suggesting that protein–protein interaction is important for biological function. Recent data predict that the tertiary structure of this C-terminal CC domain is strikingly similar to that of yeast protein She2p; furthermore, like She2p, 4/1 protein exhibits RNA-binding activity, and mutational analysis has shown that the C-terminal CC domain is responsible for RNA binding. The 4/1 protein contains a nuclear export signal. Additional microscopy studies involving leptomycin and computer prediction suggest the presence of a nuclear localization signal as well.

Highlights

Identification of host proteins involved in virus–host interactions has long been an area of intense interest for molecular virologists
To identify host factors that may play important roles in virusspecific processes, Arabidopsis thaliana and Nicotiana benthamiana cDNA libraries were screened in yeast two-hybrid system with NSm, the tubule-forming Movement proteins (MPs) of Tomato spotted wilt tospovirus (TSWV), as bait (Soellick et al, 2000; von Bargen et al, 2001; Schoelz et al, 2011)
Any functional relevance of At-4/1 for TSWV infection remains uncovered, subsequent studies have shown the 4/1 protein to be an excellent tool for studying intracellular protein trafficking and intercellular communication (Paape et al, 2006; Solovyev et al, 2013a)

Summary

Introduction

Identification of host proteins involved in virus–host interactions has long been an area of intense interest for molecular virologists. The organization and encoded protein sequences of this putative ancestral 4/1 gene are similar to the five 3’-terminal exon–introns of the tobacco 4/1 gene (Figure 1A and our unpublished data).

Results

Conclusion