Filamentous Fungal Host Strains for Consistent Protein Expression
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Solution Overview
Problem
Filamentous fungal host cell strains exhibit high variability in protein expression due to non-homologous integration and positional effects, making it difficult to reliably produce enzymes of interest with consistent characteristics.
Innovation Solution
Development of filamentous fungal host cell expression systems with disruptions in the nonhomologous recombination pathway and the use of selective markers to facilitate homologous recombination, ensuring stable and consistent expression of genes of interest by introducing nucleic acid molecules with sequences that confer selectable functions and flank chromosomal markers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-homologous integration is used for gene expression in filamentous fungi, then transformation efficiency is improved, but expression variability increases due to positional effects
Solution Approach 1:
The patent removes the harmful non-homologous recombination pathway from the fungal genome by disrupting key genes (ku80, rad50, mre11, xrs2, lig4). This extraction of the problematic recombination mechanism eliminates random integration and positional effects, forcing all integrations to occur via homologous recombination only, thereby ensuring consistent expression levels across transformants while maintaining high transformation efficiency through the use of selectable markers and optimized transformation protocols.
Solution Approach 2:
The patent changes the fundamental parameter of recombination mechanism from non-homologous to homologous by genetically modifying the host fungus. This parameter change in the recombination pathway ensures that all DNA integrations occur at predetermined locations with controlled copy numbers (typically one to three copies), eliminating the variability associated with random integration sites while preserving efficient transformation through the use of flanking homology sequences and selectable markers.
2Reliability
If multiple transformants are screened to obtain stable expression, then expression stability is improved, but time and resource consumption increase
Solution Approach 1:
The patent performs preliminary action by pre-disrupting the non-homologous recombination pathway in the host fungus before transformation. This preliminary genetic modification ensures that all subsequent transformations will occur via homologous recombination only, guaranteeing stable integration and expression from the first transformant screened. This eliminates the need for extensive screening of multiple transformants to find stable expressors, reducing both time and resource consumption while ensuring expression stability.
Solution Approach 2:
The patent uses flanking homology sequences as intermediaries to mediate precise homologous recombination events. These homology sequences (typically 40-200 bp) flanking the DNA insert serve as docking sites that guide accurate integration at predetermined locations. This intermediary mechanism ensures stable, reproducible integration without requiring screening of multiple transformants, as all integrations occur at the same controlled location with consistent copy numbers.
3Reliability
If homologous recombination is enforced for gene integration, then expression variability is reduced, but transformation complexity increases
Solution Approach 1:
The patent segments the transformation system into distinct functional components: (1) the disrupted non-homologous recombination pathway (ku80, rad50, mre11, xrs2, or lig4 disruptions), (2) the DNA construct with flanking homology sequences, (3) the selectable marker, and (4) the gene of interest. This segmentation allows each component to perform its specific function efficiently - the disrupted pathway prevents random integration, the homology sequences enable precise integration, the marker enables selection, and the gene of interest is expressed consistently. This modular approach reduces overall complexity compared to screening multiple transformants for stability.
Solution Approach 2:
The patent creates a universal transformation system that works for any gene of interest by using standardized flanking homology sequences and selectable markers. The disrupted non-homologous recombination pathway serves multiple functions: it eliminates positional effects, ensures single-copy integration, and prevents formation of heterokaryons. This multi-functional approach provides a universal platform for consistent gene expression across different genes and experiments, reducing the need for gene-specific optimization and simplifying the overall transformation process.
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
The approach results in reliable and reduced variability in protein expression, allowing for efficient screening of DNA libraries and improved assessment of variant proteins' characteristics, with at least 60% of transformants being stable and expressing proteins consistently.
Implementation Method 1
sequences with substantial homology to sequences that flank the chromosomal selectable markers; wherein the homologous sequences cause a homologous recombination event
Implementation Method 2
a disruption in one or more components of the nonhomologous recombination (NHR) pathway
Data Source
AI summary
The present disclosure relates to filamentous fungal host strains and recombinant DNA constructs for creation and use thereof. The filamentous fungal host strains are particularly useful for efficiently screening DNA libraries encoding recombinant proteins.