A FYVE zinc finger domain protein specifically links mRNA transport to endosome trafficking

Abstract

An emerging theme in cellular logistics is the close connection between mRNA and membrane trafficking. A prominent example is the microtubule-dependent transport of mRNAs and associated ribosomes on endosomes. This coordinated process is crucial for correct septin filamentation and efficient growth of polarised cells, such as fungal hyphae. Despite detailed knowledge on the key RNA-binding protein and the molecular motors involved, it is unclear how mRNAs are connected to membranes during transport. Here, we identify a novel factor containing a FYVE zinc finger domain for interaction with endosomal lipids and a new PAM2-like domain required for interaction with the MLLE domain of the key RNA-binding protein. Consistently, loss of this FYVE domain protein leads to specific defects in mRNA, ribosome, and septin transport without affecting general functions of endosomes or their movement. Hence, this is the first endosomal component specific for mRNP trafficking uncovering a new mechanism to couple mRNPs to endosomes.DOI: http://dx.doi.org/10.7554/eLife.06041.001

Fungal Morphogenesis, from the Polarized Growth of Hyphae to Complex Reproduction and Infection Structures

“…A loss of function causes no defects in general endosomal functions but causes defects in the recruitment of Rrm4, septin mRNA, and septin protein. As expected, this results in defective septin filament formation and in disturbed hyphal growth (193).…”

Endosomal assembly and transport of heteromeric septin complexes promote septin cytoskeleton formation

“…This might be needed for efficient formation of higher-order cortical filaments at the growing pole. Initially, we focused on Cdc3-GfpN because it exhibited the best biological activity, and in previous studies we have demonstrated in fluorescence recovery after photobleaching (FRAP) experiments that recovery of Cdc3-GfpN depends on Rrm4 Pohlmann et al, 2015). In this study, we were able to increase the spatial resolution and could resolve cortical filaments.…”

“…The key factor for mRNA transport is the RNA-binding protein Rrm4, which contains three RNA recognition motifs (RRM) at the N-terminus and two peptide-binding MLLE-domains (Becht et al, 2005;Pohlmann et al, 2015). The MLLE domains interact with Upa1, an endosomal component that functions in recruiting Rrm4 to Rab5a-positive endosomes (Pohlmann et al, 2015).…”

“…The MLLE domains interact with Upa1, an endosomal component that functions in recruiting Rrm4 to Rab5a-positive endosomes (Pohlmann et al, 2015). The RRMs bind target mRNAs encoding, for example, the septin Cdc3 (König et al, 2009).…”

Selective Targeting of Mobile mRNAs to Plasmodesmata for Cell-to-Cell Movement

“…The different structure motifs on 358 mobile mRNAs may recruit specific RBPs at particular stages, or reciprocally, the 359 enrolled RBPs may induce a conformational change in mRNA structure for further 360 transport (Edelmann et al, 2017). The crucial roles of RBPs in the subcellular 361 localization of mobile mRNAs may be mediated by bridging mobile mRNAs to 362 endomembrane or cytoskeleton systems or be associated with motor proteins (Takizawa 363 et al, 1997;Schnorrer et al, 2000;Pohlmann et al, 2015). Indeed, analysis of RBPs in 364 phloem exudates identified multiple putative systemic RBPs involved in 365 phloem-mediated mRNA transport (Ham et al, 2009;Li et al, 2011 …”