FAQs about our Project

Q. How is control of gene expression by chromatin different from control by transcription factors (and what are its advantages)?

 

A. Chromatin is a completely different level of gene expression control.

·        Dominant over transcription factors (resistant to noise).

·        Regional – silences domains, not individual genes (reduces the engineering required for regulation of complex multi-gene systems).

·        Memory–Alteration in gene expression lasts for multiple generations (epigenetic control).

·        Intrinsically bistable, i.e. all-or-none expression (increases parameter space over which circuits are predicted to be stable).

 

 

Q. What applications could this type of synthetic chromatin control system be used for?

 

A. To stably and permanently switch cells between different states characterized by significant differences in gene expression (i.e. cellular differentiation).

·        In bio-production–for coordinated switching between a growth phase and a production phase.

·        In bio-production–to differentiate a clonal population of cells into a distribution of subtypes that function cooperatively (“factory” with different specialized “workers”).

·        To reprogram cell fate in a highly specific manner (e.g. stem cell engineering, correction of epigenetic abnormalities in cancer cells).

·        To create cells with highly digital computational capabilities.

·        To study chromatin spreading mechanism in a quantitative and controlled way.

 

 

Q. Could this type of yeast synthetic chromatin control system be utilized in other cell types, including mammalian cells?

 

A. Yes, the approach should be transferable.

·        Core elements of this system are: initiator, covalent mark, spreading (polymerization).

·        In S. cerevisiae, covalent mark is deacetylation–we use an initiator (LexA-Sir2) that when localized deacetylates adjacent histones.  This leads to further recruitment of Sir2, which propagates the mark outward. Deacetylated chromatin adopts a “closed” conformation.

·        For higher eukaryotes, from S. pombe to human, the covalent mark is methylation, initiator is a histone methyltransferase. But in principle, a similar system should work.  Same logical design, with different catalytic functions propagating spread.