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From 2014.igem.org

Project Design

Gene Cassettes are the carriers of genetic information in our design. They are small, modular chunks of DNA containing a gene flanked by AttC sites. Cassettes, unlike plasmids, are non-replicative and so do not require extra genes to modulate or initiate replication. To create a cassette simply requires the use of primers to create half AttC sites at either end and circularizing the product through Gibson Assembly or in other ways.

As gene cassettes are non-replicative it is important that they are incorporated into an AttI site before the cell divides and the cassettes face the possibility of ejection. Therefore it is vital to have a controllable Integrase gene which can be turned on prior to the addition of gene cassettes to ensure that the cassettes are integrated before they are lost. Part pUS203 is our submission BioBrick which encodes the controllable Integrase system. We are using the araC-pBAD system from K731201 which allows us to turn on transcription of the Integrase under the activation of arabinose.

As gene cassettes enter the cell site the integrase acts to cause specific recombination between the AttC site on the cassette and an AttI site which may be present on a plasmid or the bacterial chromosome. The cassette forms a holiday junction at the recombination site.

Now that the required cassette is present in the array we can induce expression of the genes from an upstream promoter to the cassette array. A single promoter can read through multiple cassettes if a terminator is not present, allowing multiple genes to be expressed from a single signal

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