Abstract:Nanos is an RNA-binding protein that is involved in the development and maintenance of germ cells. In combination with Pumilio, Nanos binds to the 3 0 untranslated region of a messenger RNA and represses its translation. Nanos has two conserved Cys-Cys-His-Cys zinc-finger motifs that are indispensable for its function. In this study, we have determined the crystal structure of the zinc-finger domain of zebrafish Nanos, for the first time revealing that Nanos adopts a novel zinc-finger structure. In addition, N… Show more
“…For example, the UGU motif of the PRE is recognized by repeats R8 through R6. This high-resolution structure, combined with previous crystal structures of Drosophila Pum (Edwards et al, 2001) and zebrafish Nos ZFs (Hashimoto et al, 2010), allowed us to build and refine the ternary complex model.10.7554/eLife.17096.007Figure 2.Nanos embraces Pumilio and hb RNA to stabilize the ternary complex.( A ) Crystal structure of a Drosophila Nos-Pum- hb NRE2 RNA ternary complex. Pum is shown as a ribbon diagram (yellow), Nos is shown as a surface representation (blue) and hb NRE2 RNA is shown as a stick model colored by atom type.…”
Collaboration among the multitude of RNA-binding proteins (RBPs) is ubiquitous, yet our understanding of these key regulatory complexes has been limited to single RBPs. We investigated combinatorial translational regulation by Drosophila Pumilio (Pum) and Nanos (Nos), which control development, fertility, and neuronal functions. Our results show how the specificity of one RBP (Pum) is modulated by cooperative RNA recognition with a second RBP (Nos) to synergistically repress mRNAs. Crystal structures of Nos-Pum-RNA complexes reveal that Nos embraces Pum and RNA, contributes sequence-specific contacts, and increases Pum RNA-binding affinity. Nos shifts the recognition sequence and promotes repression complex formation on mRNAs that are not stably bound by Pum alone, explaining the preponderance of sub-optimal Pum sites regulated in vivo. Our results illuminate the molecular mechanism of a regulatory switch controlling crucial gene expression programs, and provide a framework for understanding how the partnering of RBPs evokes changes in binding specificity that underlie regulatory network dynamics.DOI:
http://dx.doi.org/10.7554/eLife.17096.001
“…For example, the UGU motif of the PRE is recognized by repeats R8 through R6. This high-resolution structure, combined with previous crystal structures of Drosophila Pum (Edwards et al, 2001) and zebrafish Nos ZFs (Hashimoto et al, 2010), allowed us to build and refine the ternary complex model.10.7554/eLife.17096.007Figure 2.Nanos embraces Pumilio and hb RNA to stabilize the ternary complex.( A ) Crystal structure of a Drosophila Nos-Pum- hb NRE2 RNA ternary complex. Pum is shown as a ribbon diagram (yellow), Nos is shown as a surface representation (blue) and hb NRE2 RNA is shown as a stick model colored by atom type.…”
Collaboration among the multitude of RNA-binding proteins (RBPs) is ubiquitous, yet our understanding of these key regulatory complexes has been limited to single RBPs. We investigated combinatorial translational regulation by Drosophila Pumilio (Pum) and Nanos (Nos), which control development, fertility, and neuronal functions. Our results show how the specificity of one RBP (Pum) is modulated by cooperative RNA recognition with a second RBP (Nos) to synergistically repress mRNAs. Crystal structures of Nos-Pum-RNA complexes reveal that Nos embraces Pum and RNA, contributes sequence-specific contacts, and increases Pum RNA-binding affinity. Nos shifts the recognition sequence and promotes repression complex formation on mRNAs that are not stably bound by Pum alone, explaining the preponderance of sub-optimal Pum sites regulated in vivo. Our results illuminate the molecular mechanism of a regulatory switch controlling crucial gene expression programs, and provide a framework for understanding how the partnering of RBPs evokes changes in binding specificity that underlie regulatory network dynamics.DOI:
http://dx.doi.org/10.7554/eLife.17096.001
“…3). Nanos-family members are distinguished throughout the animal kingdom by a conserved CCHC Zinc-finger motif that is required for RNA binding (Hashimoto et al, 2010). Alone, Nanos has little RNA-sequence-specific binding activity, but in all species studied it acts as a translational repressor (reviewed in Lai & King, 2013; Lai, Zhou, Luo, Fox, & King, 2011).…”
Section: Mechanisms For Protecting the Germline During The Mztmentioning
In Xenopus, the germline is specified by the inheritance of germ-plasm components synthesized at the beginning of oogenesis. Only the cells in the early embryo that receive germ plasm, the primordial germ cells (PGCs), are competent to give rise to the gametes. Thus, germ-plasm components continue the totipotent potential exhibited by the oocyte into the developing embryo at a time when most cells are preprogrammed for somatic differentiation as dictated by localized maternal determinants. When zygotic transcription begins at the mid-blastula transition, the maternally set program for somatic differentiation is realized. At this time, genetic control is ceded to the zygotic genome, and developmental potential gradually becomes more restricted within the primary germ layers. PGCs are a notable exception to this paradigm and remain transcriptionally silent until the late gastrula. How the germ-cell lineage retains full potential while somatic cells become fate restricted is a tale of translational repression, selective degradation of somatic maternal determinants, and delayed activation of zygotic transcription.
“…This zinc-finger domain was crystallized for the first time using the zebrafish Nanos (Hashimoto et al, 2010), which revealed that its basic surface is directly involved in RNA binding. In contrast to Nanos, its binding partner protein, Pumilio, is not limited to the germ line and instead is uniformly distributed e.g.…”
Nanos is a translational regulator required for the survival and maintenance of primordial germ cells. In the sea urchin, Strongylocentrotus purpuratus (Sp), Nanos 2 mRNA is broadly transcribed but accumulates specifically in the small micromere (sMic) lineage, in part because of the 3′UTR element GNARLE leads to turnover in somatic cells but retention in the sMics. Here we found that the Nanos 2 protein is also selectively stabilized; it is initially translated throughout the embryo but turned over in the future somatic cells and retained only in the sMics, the future germ line in this animal. This differential stability of Nanos protein is dependent on the open reading frame (ORF), and is independent of the sumoylation and ubiquitylation pathways. Manipulation of the ORF indicates that 68 amino acids in the N terminus of the Nanos protein are essential for its stability in the sMics whereas a 45 amino acid element adjacent to the zinc fingers targets its degradation. Further, this regulation of Nanos protein is cell autonomous, following formation of the germ line. These results are paradigmatic for the unique presence of Nanos in the germ line by a combination of selective RNA retention, distinctive translational control mechanisms (Oulhen et al., 2013), and now also by defined Nanos protein stability.
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