Co-translational Protease Cleavage for Transcription Factor Measurement
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Solution Overview
Problem
Current methods are inadequate for measuring the stochastic expression dynamics of transcription factors in real time at the single-molecule level, as existing approaches disrupt DNA binding or other essential functions when fusing fluorescent proteins to these factors.
Innovation Solution
A method involving a construct with an autoregulatory molecule fused to a cleavable substrate and a measurable marker, where a protease co-translationally cleaves the substrate, allowing the autoregulatory molecule to fold into a functional form while the marker is released for measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fluorescent protein is fused to a transcription factor for measurement, then the transcription factor expression can be detected, but the DNA binding or other essential functions of the transcription factor are disrupted
Solution Approach 1:
The transcription factor is segmented into two parts: a functional domain that remains unmodified and a separate fluorescent reporter protein. The functional domain binds to DNA without disruption, while the fluorescent reporter provides measurement capability. This segmentation resolves the contradiction by separating the measurement function from the functional function.
Solution Approach 2:
An intermediary system is introduced consisting of a separate fluorescent reporter protein and a binding interaction system. The reporter protein does not directly fuse to the transcription factor but instead uses a mediator mechanism (such as split-fluorescent protein reconstitution or proximity-based activation) to provide measurement while leaving the transcription factor's DNA binding function intact.
2Reliability
If a transcription factor is expressed at low levels to maintain physiological conditions, then gene regulation precision is maintained, but measurement signal strength is insufficient
Solution Approach 1:
Instead of directly measuring the low-abundance transcription factor, a copy or surrogate signal is generated through the fluorescent reporter system. The reporter is activated or expressed in proportion to the transcription factor activity, amplifying the measurement signal while the actual transcription factor remains at physiological low levels to maintain gene regulation precision.
Solution Approach 2:
The direct measurement approach (which would require high transcription factor levels and thus disrupt physiology) is replaced with an optical measurement system using fluorescent proteins. This substitution allows sensitive detection of low-abundance transcription factors through light emission, maintaining both physiological conditions and measurement capability.
3Productivity
If real-time measurement of transcription factor expression is implemented, then dynamic expression dynamics can be observed, but the measurement method may interfere with natural expression dynamics
Solution Approach 1:
An intermediary fluorescent reporter system is used that does not directly interfere with the transcription factor's natural function or expression dynamics. The reporter acts as a passive observer that reports transcription factor activity without altering it, enabling real-time measurement while preserving natural dynamics.
Solution Approach 2:
Direct measurement methods that would require physical manipulation or high concentrations (potentially disrupting natural dynamics) are replaced with non-invasive fluorescent protein-based optical measurement. This allows real-time monitoring of transcription factor expression dynamics without mechanical or chemical interference with the natural system.
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
Enables accurate measurement of transcription factor expression in real time without disrupting its function, providing insights into gene regulation and stochastic noise components.
Implementation Method 1
a protease capable of cleaving the cleavable substrate in the cell is expressed. In a subsequent step, the protease cleaves the cleavable substrate during translation allowing the autoregulatory molecule to fold into a functional molecule
Implementation Method 2
The measurable marker is also released and capable of being measured by standard techniques
Data Source
AI summary
A method for measuring expression of autoregulatory molecules within living cells is provided. An autoregulatory molecule and marker construct is expressed in vivo, where the marker is cleaved from the construct during translation. The method comprises the expression of a construct having an autoregulatory molecule bound to a measurable expression marker by a cleavable linker. The cleavable linker is the substrate of a protease, which acts on its substrate in vivo during translation. Cleavage during translation, allows the autoregulatory molecule to fold normally as it would in its native form. The measurable marker is released and available for detection upon cleavage by the protease. As a result, the concentration of the measurable marker is directly related to the level of expression of the autoregulatory molecule.