RNA viruses exploit host cells by co-opting host factors and lipids and escaping host antiviral responses. Previous genome-wide screens with Tomato bushy stunt virus (TBSV) in the model host yeast have identified 18 cellular genes that are part of the actin network. In this paper, we show that the p33 viral replication factor interacts with the cellular cofilin (Cof1p), which is an actin depolymerization factor. Using temperature-sensitive (ts) Cof1p or actin (Act1p) mutants at a semi-permissive temperature, we find an increased level of TBSV RNA accumulation in yeast cells and elevated in vitro activity of the tombusvirus replicase. We show that the large p33 containing replication organelle-like structures are located in the close vicinity of actin patches in yeast cells or around actin cable hubs in infected plant cells. Therefore, the actin filaments could be involved in VRC assembly and the formation of large viral replication compartments containing many individual VRCs. Moreover, we show that the actin network affects the recruitment of viral and cellular components, including oxysterol binding proteins and VAP proteins to form membrane contact sites for efficient transfer of sterols to the sites of replication. Altogether, the emerging picture is that TBSV, via direct interaction between the p33 replication protein and Cof1p, controls cofilin activities to obstruct the dynamic actin network that leads to efficient subversion of cellular factors for pro-viral functions. In summary, the discovery that TBSV interacts with cellular cofilin and blocks the severing of existing filaments and the formation of new actin filaments in infected cells opens a new window to unravel the way by which viruses could subvert/co-opt cellular proteins and lipids. By regulating the functions of cofilin and the actin network, which are central nodes in cellular pathways, viruses could gain supremacy in subversion of cellular factors for pro-viral functions.

Document Type


Publication Date


Notes/Citation Information

Published in PLOS Pathogens, v. 12, no. 2, e1005440, p. 1-32.

© 2016 Nawaz-ul-Rehman et al.

This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Digital Object Identifier (DOI)


Funding Information

This work was supported by the National Science Foundation, MCB-1517751, awarded to PDN.

journal.ppat.1005440.s001.DOC (218 kB)
S1 Materials and Methods. Supplementary Materials and Methods.

journal.ppat.1005440.s002.EPS (3481 kB)
S1 Fig. Testing Cof1p mutants for their ability to inhibit TBSV repRNA accumulation in yeast.

journal.ppat.1005440.s003.EPS (1239 kB)
S2 Fig. Over-expression of the native Cof1p inhibits TBSV repRNA accumulation in yeast.

journal.ppat.1005440.s004.TIF (488 kB)
S3 Fig. Confocal laser microscopic images of TBSV-infected plant cells expressing TBSV p33 replication protein.

journal.ppat.1005440.s005.TIF (545 kB)
S4 Fig. Confocal laser microscopic images of CIRV-infected plant cells expressing CIRV p36 replication protein.

journal.ppat.1005440.s006.TIF (431 kB)
S5 Fig. Confocal laser microscopic images of uninfected plant cells.

journal.ppat.1005440.s007.EPS (3242 kB)
S6 Fig. Enhanced co-purification of Osh6p with p33/p92 replication proteins from actin mutant yeast.

journal.ppat.1005440.s008.AVI (11790 kB)
S1 Video. 3D Super Resolution laser microscopic image of a yeast cell.