#DOTD: Alu elements

28 Aug 2017

Alu elements are the most abundant family of non-LTR TEs, namely SINEs, in the human genome. They have been in the human genome for over 60 million years + are still active (transposition-competent). Alus occur around a million times in the human genome. 

 

Alus are usually 300bp in length + their structure is a dimer of two sequences evolved from the small cytoplasmic 7SL RNA gene, with an A-rich spacer in between + terminated by an oligomer of T's.

 

Alus rely on the retrotransposition machinery of group L1 LINEs + their insertions have been associated with many diseases, such as breast cancer and diabetes.

 

They come in three flavours: AluJ, AluS and AluY, which are listed in chronological order of appearance in the genome. The AluJ family is hypothesised to be completely inactive in the human genome; a small proportion of AluS elements are still active; and the AluY group is completely active.

 

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References:

1. Cordaux, R. and Batzer, M.A., 2009. The impact of retrotransposons on human genome evolution. Nature reviews. Genetics, 10(10), p.691.

2. https://en.wikipedia.org/wiki/Alu_element

3. Bennett, E.A., Keller, H., Mills, R.E., Schmidt, S., Moran, J.V., Weichenrieder, O. and Devine, S.E., 2008. Active Alu retrotransposons in the human genome. Genome research, 18(12), pp.1875-1883.

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