FIE3 (ftz instability element 3') element
Encyclopedia
The FIE3 element is an RNA element
Cis-regulatory element
A cis-regulatory element or cis-element is a region of DNA or RNA that regulates the expression of genes located on that same molecule of DNA . This term is constructed from the Latin word cis, which means "on the same side as". These cis-regulatory elements are often binding sites for one or...

 found in the 3' UTR of the fushi tarazu mRNA.
The fushi tarazu gene is essential for the establishment of the Drosophila
Drosophila
Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" or more appropriately pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit...

 embryonic body plan. When first expressed in early embryogenesis
Embryogenesis
Embryogenesis is the process by which the embryo is formed and develops, until it develops into a fetus.Embryogenesis starts with the fertilization of the ovum by sperm. The fertilized ovum is referred to as a zygote...

, fushi tarazu mRNA is uniformly distributed over most of the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

. Subsequently, fushi tarazu mRNA expression rapidly evolves into a pattern of seven stripes that encircle the embryo. The instability of fushi tarazu mRNA may contribute to the localization of this pattern of expression
Gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...

, but this is unlikely to be a dominant effect since the 744 base-pair ftz zebra stripe element can drive the ectopic expression of a reporter construct (with mRNA structure entirely unrelated to the ftz transcript) in a qualitatively highly similar pattern. Experiments provide evidence for at least two destabilising elements in the fushi tarazu mRNA, one located within the 5' one-third of the mRNA and the other near the 3' end (termed FIE3 for ftz instability element 3'). The FIE3 lies within a 201-nucleotide
Nucleotide
Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...

 sequence just upstream of the polyadenylation
Polyadenylation
Polyadenylation is the addition of a poly tail to an RNA molecule. The poly tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In eukaryotes, polyadenylation is part of the process that produces mature messenger RNA for translation...

 signal and can act autonomously to destabilise a heterologous mRNA. Further deletion constructs identified an essential 68-nucleotide element within the FIE3. Although this element is predicted to contain a secondary structure, it also contains a GU rich sequence (UGUUUUGUUU) that is simlar to GU rich instabilty elements subsequently identified in other systems.
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