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Team:UCSF/Synthetic Chromatin Design
From 2008.igem.org
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Synthetic Chromatin Bit
The Yeast Native System
The specifics of heterochromatin (e.g. histone tail mark, binding proteins etc.) varies by organism, but there seems to be a conserved general mode of spreading. First, a histone modifier (pink half circle) is recruited to a site of initiation, where it makes local histone tail modifications. These modified tails serve as sites of recruitment for binding proteins (yellow hexagons) which then recruit more histone modifiers. Thus, positive feedback at the level of histone tail modification propagates silencing outward. In S. cerevisiae, the histone modifier is Sir2 (Silent Information Regulator 2), a histone de-acetylase that primarily targets H4K16. This mark is bound by Sir3 and Sir4, which then recruit more Sir2.
Design of our Yeast Synthetic Chromatin System
To re-direct silencing to the locus of our choice in S. cerevisiae, we fused the LexA DNA binding domain to Sir2. This construct is induced by the addition of galactose to the media, and targeted to LexA operators, which we inserted at various positions around a reporter gene (GFP).
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