Epigenome Modifier Construct for Stable Gene Silencing
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Solution Overview
Problem
Current gene silencing methods, such as RNA interference and designer nucleases, face challenges like low efficiency, off-target effects, and toxicity, particularly in achieving stable and long-term silencing of highly expressed genes and in clinical applications involving primary human cells.
Innovation Solution
A 'designer epigenome modifier' construct combining a Krüppel-associated box zinc finger protein, a TALE-based DNA binding domain, and DNA methyltransferases DNMT3A and Dnmt3L, which induces epigenetic modifications to specifically silence target genes by methylation and histone modification, allowing for stable and long-term gene silencing with reduced off-target activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RNA interference or designer nucleases are used for gene silencing, then gene expression can be reduced, but efficiency is low and off-target effects occur
Solution Approach 1:
The construct is divided into distinct functional modules: a DNA binding domain (TALE or zinc finger) that specifically recognizes the target gene sequence, and a DNA methyltransferase domain (DNMT3A and/or Dnmt3L) that catalyzes methylation. This segmentation allows independent optimization of targeting specificity and silencing efficiency, reducing off-target effects while maintaining high efficiency.
Solution Approach 2:
The invention applies epigenetic modification locally at the target gene promoter region through sequence-specific DNA binding. The DNA methyltransferase is recruited precisely to the target locus by the binding domain, ensuring that methylation and gene silencing occur only at the intended location without affecting other genomic regions, thereby eliminating off-target effects.
2Duration of action of moving object
If current gene silencing methods are used, then gene expression can be inhibited, but the silencing is not stable over cell divisions
Solution Approach 1:
The construct performs preliminary epigenetic marking by establishing DNA methylation and histone modifications at the target gene promoter before cell division occurs. These epigenetic marks are set in advance and are then heritably maintained through subsequent cell divisions by endogenous maintenance methyltransferases, ensuring stable and long-lasting gene silencing without requiring continuous presence of the construct.
Solution Approach 2:
The invention leverages the cell's own epigenetic maintenance machinery. Once the construct establishes de novo methylation patterns at the target locus, the cell's endogenous DNMT1 and other maintenance factors automatically preserve these marks through cell divisions. This self-service mechanism ensures stable inheritance of the silenced state without continuous external intervention.
3Reliability
If RNA interference is used for gene silencing, then gene expression can be reduced, but toxicity occurs due to interference with endogenous mechanisms
Solution Approach 1:
The invention replaces the RNA interference mechanism (which operates at the RNA level and interferes with endogenous RNA processing) with an epigenetic modification mechanism that acts at the DNA level. By using DNA methyltransferases to establish repressive chromatin marks, the system achieves gene silencing through a fundamentally different biochemical pathway that does not interfere with cellular RNA metabolism, thereby eliminating toxicity associated with RNAi.
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 construct achieves efficient and stable silencing of target genes, including HIV co-receptors, with minimal off-target effects, maintaining epigenetic changes over cell divisions and offering a safer, more effective approach for therapeutic applications.
Implementation Method 1
Epigenetic changes of the genome comprise changes in DNA methylation and histone modification... DNMT3A, DNMT3B and DNMT3L that induce de novo methylation of a cytosine base to methylated 5-methylcytosine
Implementation Method 2
Furthermore, the histones on which the DNA is bound are subject to many different post-translational modifications including acetylation, methylation, phosphorylation and ubiquitination
Data Source
AI summary
Herein described is a construct for epigenomic modification of genes composed of: (a) a Krüppel-associated box zinc finger protein or homologous, (b) a DNA region capable of binding to the target gene or homologous, (c) a human DNA methyltransferase DNMT3A or homologous and (d) a murine DNA methyltransferase Dnmt3L or homologous, wherein components a), b), c) and d) are linked to each other either directly or via at least one linker. The construct is a designer epigenome modifier that can be used to silence genes coding for a protein in leukocytes that avoids the internalization of HI viruses in immune cells.