Inducible CRISPR System with Fusion Promoter for HIV Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current CRISPR systems face challenges in controlling the expression of Cas9 and guide RNA, leading to off-target effects and uncontrolled silencing of genes, particularly in therapeutic applications like HIV treatment, where conditional and cell-type specific expression is desirable to avoid harmful side effects and viral escape mutations.
Innovation Solution
An inducible CRISPR system is developed with a fusion promoter that drives the expression of both Cas and guide sequences in response to a specific inducer, such as HIV-1 TAT, allowing for controlled and tissue-specific or viral-specific activation of the CRISPR complex, using a Pol II promoter associated with HIV-1 LTR and incorporating catalyzing RNAs like ribozymes for enhanced regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If constitutive Pol III promoters are used for gRNA expression, then continuous gRNA production is achieved, but uncontrolled expression leads to off-target effects and mutations
Solution Approach 1:
The patent transitions from static constitutive expression to dynamic inducible expression by incorporating a tetracycline-responsive promoter (Tet-On) that can be activated or deactivated based on experimental needs. This allows controlled gRNA production only when required, preventing continuous off-target effects while maintaining productivity when activated.
Solution Approach 2:
The patent implements feedback control through the tetracycline-responsive promoter system, where the presence or absence of tetracycline ligand directly regulates promoter activity. This feedback mechanism ensures gRNA expression occurs only under specific conditions, preventing uncontrolled off-target effects while maintaining continuous production capability when activated.
2Ease of operation
If Pol II promoters are used for Cas9 expression with tetracycline control, then inducible Cas9 expression is achieved, but gRNA expression remains constitutive causing coordination problems
Solution Approach 1:
The patent merges the control of Cas9 and gRNA expression under a single tetracycline-responsive promoter system. Both genes are placed under the same promoter, allowing simultaneous inducible expression of both components, eliminating the coordination problems arising from separate constitutive and inducible systems.
Solution Approach 2:
The patent creates a universal promoter system that can regulate multiple CRISPR components (Cas9 and gRNA) through a single tetracycline-responsive element. This multi-functional promoter system simplifies the overall device by providing unified control for multiple functions that would otherwise require separate regulatory mechanisms.
3Adaptability or versatility
If CRISPR systems are expressed in all cell types, then broad therapeutic coverage is achieved, but non-specific silencing causes toxicity and loss of gene function
Solution Approach 1:
The patent applies local quality control by using tissue-specific promoters (such as Cre recombinase-driven promoters active in specific cell types) to restrict CRISPR expression to particular tissues or cell types. This ensures therapeutic coverage is achieved only where needed, preventing non-specific silencing and toxicity in other tissue types.
Solution Approach 2:
The patent implements dynamic control of CRISPR expression through inducible promoter systems that can be activated or deactivated based on temporal and spatial requirements. This allows the system to adapt its expression pattern to match specific therapeutic needs, providing broad coverage when activated while preventing harmful non-specific activity when inactive.
Data Source
AI summary
The invention pertains to an inducible CRISPR system for controlling expression of a CRISPR complex with an inducible fusion promoter. One embodiment of the invention provides HIV LTR-minimal Drosophila hsp70 fusion promoter that can be used for inducible co-expression of gRNA and Cas9 in HIV-infected cells to target cellular cofactors such as Cyclin T1. A single introduction of such embodiment leads to sustained suppression of HIV replication in stringent, chronically infected HeLa-CD4 cell lines as well as in T-cell lines. In another embodiment, the invention further relates to enhancement of HIV suppression by incorporating cis-acting ribozymes immediately upstream of the gRNA in the inducible CRISPR system construct. The inducible fusion promoter is adaptable for other tissue- or cell-type specific expression of the inducible CRISPR system.