A split intein T7 RNA polymerase for transcriptional AND-logic

Schaerli, Yolanda; Gili, Magui; Isalan, Mark

doi:http://dx.doi.org/10.1093/nar/gku884

A split intein T7 RNA polymerase for transcriptional AND-logic

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Schaerli Y, Gili M, Isalan M. A split intein T7 RNA polymerase for transcriptional AND-logic. Nucleic Acids Res. 2014 Oct 29;42(19):12322-8. DOI: 10.1093/nar/gku884

Abstract

Synthetic biology has developed numerous parts for building synthetic gene circuits. However, few parts have been described for prokaryotes to integrate two signals at a promoter in an AND fashion, i.e. the promoter is only activated in the presence of both signals. Here we present a new part for this function: a split intein T7 RNA polymerase. We divide T7 RNA polymerase into two expression domains and fuse each to a split intein. Only when both domains are expressed does the split intein mediate protein trans-splicing, yielding a full-length T7 RNA polymerase that can transcribe genes via a T7 promoter. We demonstrate an AND gate with the new part: the signal-to-background ratio is very high, resulting in an almost digital signal. This has utility for more complex circuits and so we construct a band-pass filter in Escherichia coli. The split intein approach should be widely applicable for engineering artificial gene circuit parts.