page_title: Alu element
section_title: Sequence features
hierarchical_section_title: Alu element / Sequence features
caption_attribution_description: English: Genetic structure of murine LINE1 and SINEs. Bottom: proposed structure of L1 RNA-protein (RNP) complexes. ORF1 proteins form trimers, exhibiting RNA binding and nucleic acid chaperone activity.
context_page_description: An Alu element is a short stretch of DNA originally characterized by the action of the Arthrobacter luteus restriction endonuclease. Alu elements are the most abundant transposable elements, containing over one million copies dispersed throughout the human genome. Alu elements were thought to be selfish or parasitic DNA, because their sole known function is self reproduction. However they are likely to play a role in evolution and have been used as genetic markers. They are derived from the small cytoplasmic 7SL RNA, a component of the signal recognition particle. Alu elements are highly conserved within primate genomes and originated in the genome of an ancestor of Supraprimates.
  Alu insertions have been implicated in several inherited human diseases and in various forms of cancer.
  The study of Alu elements has also been important in elucidating human population genetics and the evolution of primates, including the evolution of humans.
context_section_description: Two main promoter "boxes" are found in Alu: a 5' A box with the consensus TGGCTCACGCC, and a 3' B box with the consensus GWTCGAGAC (IUPAC nucleic acid notation). tRNAs, which are transcribed by RNA polymerase III, have a similar but stronger promoter structure. Both boxes are located in the left arm.
  Alu elements contain four or fewer retinoic acid response element hexamer sites in its internal promoter, with the last one overlapping with the "B box". In this 7SL (SRP) RNA example below, functional hexamers are underlined using a solid line, with the non-functional third hexamer denoted using a dotted line:
  GCCGGGCGCGGTGGCGCGTGCCTGTAGTCCCagctACTCGGGAGGCTGAGGCTGGAGGATCGCTTGAGTCCAGGAGTTCTGGGCTGTAGTGCGCTATGCCGATCGGAATAGCCACTGCACTCCAGCCTGGGCAACATAGCGAGACCCCGTCTC. 
  The recognition sequence of the Alu I endonuclease is 5' ag/ct 3'; that is, the enzyme cuts the DNA segment between the guanine and cytosine residues (in lowercase above).
caption: Genetic structure of murine LINE1 and SINEs, including Alu.
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