Staufen is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

product of a maternally expressed

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

first identified in ''

Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (the taxonomic order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly" or "pomace fly". Starting with Ch ...

.'' The protein has been implicated in helping regulate genes important in determination of gradients that set up the anterior posterior axis such as

bicoid Homeotic protein bicoid is encoded by the ''bcd'' maternal effect gene in ''Drosophilia''. Homeotic protein bicoid concentration gradient patterns the anterior-posterior (A-P) axis during ''Drosophila'' embryogenesis. Bicoid was the first prot ...

and

oskar Oskar may refer to: * oskar (gene), the Drosophila gene * Oskar (given name) Oscar or Oskar is a masculine given name of Irish origin. Etymology The name is derived from two elements in Irish: the first, ''os'', means "deer"; the second element, ' ...

. Staufen proteins, abbreviated Stau, are necessary for cell localization during the oogenesis and

zygotic A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicellula ...

development. It is involved in targeting of the

messenger RNA In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein. mRNA is created during the p ...

encoding these genes to the correct pole of the egg cell. Human

homolog In biology, homology is similarity due to shared ancestry between a pair of structures or genes in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats and birds, the arms of prima ...

s of this protein include STAU1 and STAU2.

Forms

Staufen proteins are categorized under a family of double stranded

RNA-binding protein RNA-binding proteins (often abbreviated as RBPs) are proteins that bind to the double or single stranded RNA in cells and participate in forming ribonucleoprotein complexes. RBPs contain various structural motifs, such as RNA recognition motif ( ...

s. Many

homologs A couple of homologous chromosomes, or homologs, are a set of one maternal and one paternal chromosome that pair up with each other inside a cell during fertilization. Homologs have the same genes in the same locus (genetics), loci where they pr ...

of Staufen proteins exist depending on the organism. The mammalian

of Staufen include STAU1 and STAU2. The gene encoding the STAU1 protein is found along the long arm of

chromosome 20 Chromosome 20 is one of the 23 pairs of chromosomes in humans. Chromosome 20 spans around 66 million base pairs (the building material of DNA) and represents between 2 and 2.5 percent of the total DNA in cells. Chromosome 20 was fully sequenced ...

, while the gene encoding STAU2 is found on

chromosome 8 Chromosome 8 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 8 spans about 145 million base pairs (the building material of DNA) and represents between 4.5 and 5.0% of the total DNA ...

. These proteins are identified by the presence of double-stranded RNA binding domains (dsRNA- binding domains), which functions to bind the protein to double-stranded secondary structure RNAs. These two

orthologues Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a sp ...

are produced in several different isoforms following pre mRNA splicing. STAU1 is predominantly expressed in most cell types, while STAU2 is conserved the brain, with low level expression in other cell tissues. Stauffen_Yu_etal

Functions

Staufen proteins are encoded and produced very early in

oogenesis Oogenesis, ovogenesis, or oögenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated in the embryonic stage. O ...

. At the primary stages of oogenesis, Staufen mRNA is evenly disbursed throughout the

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...

of the cell. As the oocyte develops, the proteins condense at the anterior margins and the posterior pole of the egg cell. In ''Drosophila'' the proteins are necessary for the translating and transporting ''

'' mRNA to the posterior pole of the oocyte. Similarly Staufen proteins are also part of a multistep process that localizes ''

Bicoid Homeotic protein bicoid is encoded by the ''bcd'' maternal effect gene in ''Drosophilia''. Homeotic protein bicoid concentration gradient patterns the anterior-posterior (A-P) axis during ''Drosophila'' embryogenesis. Bicoid was the first prot ...

'' mRNA to the anterior end of the early embryo, and these proteins are also responsible for asymmetric dispersion of ''prospero'' mRNA as the embryonic neuroblast divides. In mammals, the STAU proteins contain a microtubule-binding domain, giving the protein the capability to bind to

Tubulin Tubulin in molecular biology can refer either to the tubulin protein superfamily of globular proteins, or one of the member proteins of that superfamily. α- and β-tubulins polymerize into microtubules, a major component of the eukaryotic cytoske ...

. Research has also shown that these proteins maintain an association with the Rough endoplasmic reticulum (RER), suggesting that transport of mRNA through the use of Staufen proteins is facilitated via the microtubule network to the rough endoplasmic reticulum.

References

Proteins Drosophila melanogaster genes {{protein-stub