Directed Evolution via Conditional Mutagenesis Control
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Solution Overview
Problem
Current methods for directed evolution of bacteriophage, such as PACE, face challenges in propagating crippled phages and inducing mutagenesis, leading to unwanted mutation rates and infection responses, which limit the efficiency and control of protein engineering.
Innovation Solution
The implementation of Mutagenesis Selection (M-Selection) system, where the mutation rate is lowered in response to the desired activity of the evolving protein, allowing for more faithful reproduction of phage with the desired activity and reducing the risk of error catastrophe, without externally induced mutagenesis or incorporation of phage genes into host plasmids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If externally induced mutagenesis is used to rapidly sample evolutionary landscape, then mutation rate increases and evolution speed improves, but unwanted mutations accumulate in both host cells and virions reducing reliability
Solution Approach 1:
The patent applies local quality by making mutagenesis conditional rather than universal. Mutagenesis is localized to occur only in infected host cells during specific evolutionary cycles, while uninfected cells maintain normal mutation rates. This is achieved through conditional expression of mutagenic components that are activated only under specific conditions (infection state), allowing different parts of the system (infected vs uninfected cells) to have different mutation rates appropriate to their function.
Solution Approach 2:
The patent implements dynamics by making the mutation rate adjustable and conditional rather than fixed. The mutation rate can be dynamically modulated based on the evolutionary stage and selection pressure. During phases requiring exploration of new genetic space, mutagenesis is activated; during phases requiring stabilization of beneficial mutations, mutagenesis is reduced or eliminated. This dynamic control allows the system to adapt mutation rates to current evolutionary needs.
2Adaptability or versatility
If crippled phage are used to propagate evolving proteins, then protein engineering flexibility improves, but propagation difficulties increase
Solution Approach 1:
The patent uses an intermediary approach by introducing a helper phage or providing essential functions in trans through the host cell. The crippled phage lacks certain essential genes but these functions are supplied by an external source (helper phage or host), allowing the crippled phage to propagate while still carrying the evolving protein of interest. This intermediary solution enables the use of crippled phage for their versatility while overcoming their propagation limitations.
Solution Approach 2:
The patent applies segmentation by dividing the phage genome into essential functions (provided by helper or host) and evolving functions (carried by crippled phage). This separation allows independent optimization: the helper provides stable, essential functions for propagation, while the crippled phage carries the flexible, evolving protein sequences. This functional segmentation resolves the contradiction between needing complete functions for propagation and needing modified functions for engineering flexibility.
3Reliability
If high flow rates are used in PACE system, then mutant accumulation is reduced, but system complexity and control difficulty increase
Solution Approach 1:
The patent implements self-service by allowing the system to automatically regulate mutation rates through intrinsic feedback mechanisms rather than requiring external flow rate control. The mutagenesis system responds to cellular conditions, infection state, or genetic markers to automatically adjust mutation rates. This self-regulation eliminates the need for complex external flow control systems while maintaining effective mutant accumulation control through biological feedback loops.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables controlled, high mutation rates for directed evolution, reduces the propagation difficulties of crippled phages, and avoids premature infection responses, allowing for a broader range of flow rates and extended access to the evolutionary landscape, ensuring the system does not get trapped at local fitness peaks.
Implementation Method 1
the mutation rate decreases proportionally in response to the production of the evolved gene product comprising the desired activity
Data Source
AI summary
The present invention relates to methods and systems for the directed evolution of macromolecules. The methods involve increasing the mutation rate of an evolving organism comprising a gene of interest that encodes a gene product lacking a desired activity, whereby a mutated gene of interest is produced that encodes an evolved gene product comprising the desired activity and causing a suppression of mutagenesis. The systems comprise an evolving organism comprising a gene of interest encoding a gene product to be evolved, a host organism, and optionally, a lagoon, a cellstat and/or a suitable growth medium.