Recently, (Tilsner et al

Recently, (Tilsner et al.,2013) showed the membrane-associated replication complex of potato virus X (PVX) are compartmentalized at PDs. to contain the viral RNA-dependent RNA polymerase and viral RNA. Symplasmic movement of TuMV may thus be achieved in the form of a membrane-associated viral RNA complex induced by 6K2. Keywords:plant RNA virus, potyvirus, replication complex, membrane association, intercellular movement == Introduction == Plant viruses encode movement proteins (MPs) that interact with plasmodesmata (PD) to achieve intercellular spread of virus infection (reviewed in Niehl and Heinlein,2011). Several viral and host proteins that are involved in intra- and intercellular movement of plant viruses have been identified. These include MPs, host secretory pathway components and actomyosin motors (reviewed in Schoelz et al.,2011). However, the nature of the viral entity that crosses over the cell barrier of the infected cell Rabbit polyclonal to ZNF76.ZNF76, also known as ZNF523 or Zfp523, is a transcriptional repressor expressed in the testis. Itis the human homolog of the Xenopus Staf protein (selenocysteine tRNA genetranscription-activating factor) known to regulate the genes encoding small nuclear RNA andselenocysteine tRNA. ZNF76 localizes to the nucleus and exerts an inhibitory function onp53-mediated transactivation. ZNF76 specifically targets TFIID (TATA-binding protein). Theinteraction with TFIID occurs through both its N and C termini. The transcriptional repressionactivity of ZNF76 is predominantly regulated by lysine modifications, acetylation and sumoylation.ZNF76 is sumoylated by PIAS 1 and is acetylated by p300. Acetylation leads to the loss ofsumoylation and a weakened TFIID interaction. ZNF76 can be deacetylated by HDAC1. In additionto lysine modifications, ZNF76 activity is also controlled by splice variants. Two isoforms exist dueto alternative splicing. These isoforms vary in their ability to interact with TFIID into non-infected ones is not clear. For some icosahedral viruses, viral particles may transit through MP-induced tubules that go Ecabet sodium through PDs for their delivery into non-infected cells (van Lent et al.,1991; Pouwels et al.,2003; Amari et al.,2011; Chen et al.,2012). In the case of tobacco mosaic virus (TMV), a filamentous virus, it has been proposed that non-encapsidated infectious RNA molecules associated with MPs are being transported, possibly as an intact viral replication complex (VRC) (Kawakami et al.,2004). The exact composition of this RNA-protein complex has yet to be defined, in particular the contribution of other viral proteins and host components (e.g., proteins and lipids). The genome of potyviruses is a single ~10 kb RNA molecule that codes for a polyprotein, which is processed into ten mature proteins. In addition to polyprotein-derived polypeptides, an ~7 kDa protein termed PIPO is produced in infected cells (Chung et al.,2008) and is also found as a trans-frame protein consisting of the amino-terminal half of P3 fused to PIPO (P3N-PIPO) (Vijayapalani et al.,2012). Potyviruses have no designated MP but many viral proteins have been reported to have MP-related functions. For instance, HCPro and the coat protein (CP) can increase the size exclusion limit (SEL) of PDs (Rojas et al.,1997). In addition, CP and the cylindrical inclusion (CI) protein are required for virus intercellular movement (Dolja et al.,1994,1995; Carrington et al.,1998). These data showed that the core domain of CP provides a function essential during cell-to-cell movement and that the variable N- and C-terminal regions exposed on the virion surface are necessary for long distance transport. CI is further associated with PD, producing conical structures that extend through PD (Rodriguez-Cerezo et al.,1997; Roberts et al.,1998). The targeting of CI to PD is mediated by P3N-PIPO (Wei et al.,2010), which itself is targeted to the plasma membrane through an interaction with the host protein PCaP1 (Vijayapalani et al.,2012). The relationship of these viral proteins with viral RNA was, however, not investigated in the above studies. One protein that may mediate the association of viral RNA with the above proteins is the 6K2protein. TuMV infection leads to Ecabet sodium significant rearrangements of the early secretory pathway of the host cell. The infection is associated with the formation of Ecabet sodium at least two distinct types of sub-cellular compartments induced by the membrane-associated viral protein 6K2: a perinuclear globular structure and motile cortical vesicular structures (Grangeon et al.,2012). The perinuclear globular structure contains endoplasmic reticulum (ER), Golgi, COPII coatomers and chloroplasts. The motile vesicular structures are derived from the globular structure and move along transvacuolar and cortical ER. These vesicles contain viral RNA, replication viral proteins and host factors (Beauchemin and Laliberte,2007; Beauchemin et al.,2007; Dufresne et al.,2008; Thivierge et al.,2008; Cotton et al.,2009; Huang et al.,2010). Latranculin B, which disrupts microfilaments, stops intracellular movement of 6K2vesicles (Cotton et al.,2009), and TuMV intercellular movement (Agbeci et al.,2013). Thus, the 6K2vesicles are involved in the movement of viral RNA. Plant RNA viruses induce the remodeling of the secretory pathway (Schaad et al.,1997; Wei and Wang,2008; Welsch et al.,2009; Cui et al.,2010; Bamunusinghe et al.,2011; Patarroyo et al.,2012; Linnik et al.,2013) or of organelles such as chloroplasts (Prod’homme et al.,2001,2003; Jonczyk et al.,2007), mitochondria (Kopek et al.,2007; Hwang et al.,2008) and peroxisomes (McCartney et al.,2005) for viral replication. These quasi-organelles are often referred to as virus factories and harbor VRCs. Virus factories are, however, more than replication complexes associated with membranes. It has been suggested that replication and intercellular movement of some plant viruses are coordinated events that are mediated by membrane-associated motile vesicular structures (Tilsner and Oparka,2012; Tilsner.