D. melanogaster gene mago nashi , abbreviated as mago , encodes a product involved in
regulation of oskar mRNA localization which is expressed in the ovary (nurse cell and oocyte ).
Swidzinski JA, et al reported molecular characterization and expression analysis of a highly
conserved rice mago nashil homolog.
Le Hir H, et al 2001 reported that the protein Mago provides a link between splicing and mRNA
Localization.
The proteins Mago and Y14 are evolutionarily conserved binding partners. Y14
is a component of the exon-exon junction complex (EJC), deposited by the
spliceosome upstream of messenger RNA (mRNA) exon-exon junctions. The EJC is
implicated in post-splicing events such as mRNA nuclear export and
nonsense-mediated mRNA decay. Drosophila Mago is essential for the
localization of oskar mRNA to the posterior pole of the oocyte, but the
functional role of Mago in other species is unknown. Mago is a
bona fide component of the EJC. Like Y14, Mago escorts spliced mRNAs to the
cytoplasm, providing a direct functional link between splicing and the
downstream process of mRNA localization. Mago/Y14 heterodimers are essential
in cultured Drosophila cells. Taken together, these results suggest that, in
addition to its specialized function in mRNA localization, Mago plays an
essential role in other steps of mRNA metabolism.
Mago Nashi, a protein initially shown to be essential in the development of the
Drosophila oocyte, is highly conserved among species and shows no homology to
any other known cellular proteins. The rice Mago Nashi protein shares at least 73%
amino acid identity with all known animal homologs. Genomic DNA gel blot
analysis indicates that two copies of the mago nashi gene exist in the rice genome,
one of which has identical intron positions to those found in an Arabidopsis
homolog. mago nashi is expressed in root, leaf and developing seed tissue as
determined by RNA and protein gel blot analysis. Evidence from Drosophila,
Caenorhabditis elegans and human studies of Mago Nashi suggests that a major
function of this protein is its involvement in RNA localization. The highly
conserved amino acid sequence of all Mago Nashi protein homologs across
kingdoms suggests that the plant version of this protein may similarly be involved
in RNA localization.
NCBI Summary:
Drosophila that have mutations in their mago nashi (grandchildless) gene produce progeny with defects in germplasm assembly and germline development. This gene encodes the mammalian mago nashi homolog. In mammals, mRNA expression is not limited to the germ plasm, but is expressed ubiquitously in adult tissues and can be induced by serum stimulation of quiescent fibroblasts.
General function
RNA binding
Comment
Naoyuki Kataoka, et al 2001 reported that Magoh, a human homolog of Drosophila mago nashi
protein, is a component of the splicing-dependent
exonexon junction complex.
The RNA-binding protein Y14 binds preferentially to mRNAs produced by splicing and is a component of a
multiprotein complex that assembles 20 nucleotides upstream of exonexon junctions. This complex probably has
important functions in post-splicing events including nuclear export and nonsense-mediated decay of mRNA. The authors identified magoh, a human homolog of the Drosophila mago nashi gene product, as a novel component
of the complex. Magoh binds avidly and directly to Y14 and TAP, but not to other known components of the complex,
and is found in Y14-containing mRNPs in vivo. Importantly, magoh also binds to mRNAs produced by splicing
upstream (20 nucleotides) of exon exon junctions and its binding to mRNA persists after export. These experiments
thus reveal specific proteinprotein interactions among the proteins of the splicing-dependent mRNP complex and
suggest an important role for the highly evolutionarily conserved magoh protein in this complex.
Cellular localization
Cytoplasmic
Comment
Ovarian function
Oogenesis
Comment
Newmark PA, et al reported that
mago nashi mediates the posterior follicle cell-to-oocyte signal to
organize axis formation in Drosophila.
Establishment of the anteroposterior and dorsoventral axes in the Drosophila egg
chamber requires reciprocal signaling between the germ line and soma. Upon
activation of the Drosophila EGF receptor in the posterior follicle cells, these
cells signal back to the oocyte, resulting in a reorganization of the oocyte
cytoplasm and anterodorsal migration of the oocyte nucleus. Mago nashi (mago) encodes an evolutionarily conserved protein that
must be localized within the posterior pole plasm for germ-plasm assembly and
Caenorhabditis elegans mago is a functional homologue of Drosophila mago. In
the absence of mago+ function during oogenesis, the anteroposterior and
dorsoventral coordinates of the oocyte are not specified and the germ plasm fails
to assemble.
Expression regulated by
Comment
Ovarian localization
Oocyte
Comment
The products of at least 11 maternal effect genes have been shown to be essential for proper
germ plasm assembly in Drosophila melanogaster embryos. Zhao XF, et al report the isolation and
characterization of the mammalian counterpart for one of these genes (named MAGOH for mago
nashi homologue). The predicted amino acid sequence of mouse and human MAGOH are
completely identical; MAGOH homologues from the nematode Caenorhabditis elegans and rice
grain Oryza sativa also show a remarkable degree of amino acid conservation. MAGOH was
mapped to chromosome 1p33-p34 in the human and a syntenic region of chromosome 4 in the
mouse. Of note, MAGOH mRNA expression is not limited to germ plasm, but is expressed
ubiquitously in adult tissues and can be induced by serum stimulation of quiescent fibroblasts.