Rice University researchers have found a way to divide and modify enzymes to create what amounts to a genetic logic gate.
Biochemist Matthew Bennett and graduate student David Shis created a library of AND gates by mutating a protein from a bacterial virus. The well-understood protein known as T7 RNA polymerase (RNAP) is a strong driver of transcription in cells.
Their discovery should help overcome a bottleneck in the development of synthetic gene networks that mimic digital circuitry. These networks could become diagnostic systems that look for signs of disease and, perhaps, gene therapies to find and treat disease in one step.
The research appeared online this week in the Proceedings of the National Academy of Sciences.
"AND logic gates are normally found in electronics: You have a circuit with two inputs and one output," said Bennett, an assistant professor of biochemistry and cell biology. "In an AND gate, if the two wires leading to the gate are both on, then the output is also on. If either one or both are off, then the output is turned off."
Few options have been available to researchers seeking reliable and flexible components for their synthetic circuits. The library of AND gates created at Rice should add significantly to the toolbox available to build larger and more complex gene circuits, Bennett said.
In its native, full-length state, T7 RNAP turns on genes that have a specific "promoter," or target DNA sequence. The Rice researchers found they could program DNA to express the RNAP in two pieces, which could be manipulated via point mutations to target different promoters in a host cell. "The two pieces of the RNAP might even be made in different parts of the cell and they'll still find each other," Bennett said. "They have an affinity for each other, and once they combine, they'll work together as if they hadn't been split."
The enzyme carried out its function only when both h
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