Source 1primary paper2025MED
Toolkit/Cas6 binding site
Cas6 binding site
Also known as: CBS
Taxonomy: Mechanism Branch / Component. Workflows sit above the mechanism and technique branches rather than replacing them.
Summary
its cognate stem-loop RNA (Cas6 binding site, termed CBS)
Usefulness & Problems
Why this is useful
CBS is the cognate stem-loop RNA element used with EcCas6/dEcCas6 in the STAR system. The abstract states that CBS guides can recruit dEcCas6-toxins.; recruiting dEcCas6-toxin fusions; guide architecture for STAR
Source:
CBS is the cognate stem-loop RNA element used with EcCas6/dEcCas6 in the STAR system. The abstract states that CBS guides can recruit dEcCas6-toxins.
Source:
recruiting dEcCas6-toxin fusions
Source:
guide architecture for STAR
Problem solved
CBS provides the RNA recognition element that enables recruitment of dEcCas6-toxin fusions to target transcripts.; provides a recruitable RNA element for dEcCas6-based targeting
Source:
CBS provides the RNA recognition element that enables recruitment of dEcCas6-toxin fusions to target transcripts.
Source:
provides a recruitable RNA element for dEcCas6-based targeting
Problem links
provides a recruitable RNA element for dEcCas6-based targeting
LiteratureCBS provides the RNA recognition element that enables recruitment of dEcCas6-toxin fusions to target transcripts.
Source:
CBS provides the RNA recognition element that enables recruitment of dEcCas6-toxin fusions to target transcripts.
Published Workflows
Objective: Engineer a hypercompact programmable RNA degrader that preserves efficient transcript knockdown while improving delivery compatibility and reducing off-target activity.
Why it works: The workflow combines small toxin RNases with a dEcCas6-CBS recruitment system so that compact components can be assembled into a programmable RNA degrader. The abstract states that CBS can be tuned for processing while retaining conserved binding, which supports guide-based recruitment of dEcCas6-toxins.
substrate-specific toxin endoribonuclease cleavagedEcCas6 recruitment to CBS-containing guide architectureCBS-mediated targeting and recruitmentexcavation and evolution of small toxin endoribonucleasesintegration of dEcCas6 with CBS guide designexperimental tuning of CBS processing and binding
Stages
- 1.Excavation and evolution of small toxin endoribonucleases(library_design)
This stage provides small catalytic modules intended to support miniature RNA degrader design.
Selection: Identify and engineer small toxin endoribonucleases with simple RNA cleavage motifs for use as compact degradative modules.
- 2.Integration of toxin modules with dEcCas6-CBS architecture(library_build)
This stage creates the STAR architecture by combining catalytic toxin modules with a recruitable RNA-targeting module.
Selection: Assemble engineered toxin modules with catalytically dead EcCas6 and CBS to create hypercompact transcript degraders.
- 3.CBS tuning for processing and binding(functional_characterization)
The abstract states that CBS tuning lays the foundation for designing guides that effectively recruit dEcCas6-toxins.
Selection: Optimize CBS for EcCas6 processing while maintaining EcCas6 and dEcCas6 binding needed for recruitment.
- 4.Mammalian-cell performance evaluation(confirmatory_validation)
This stage confirms that the compact degrader functions on cytoplasmic and nuclear transcripts in mammalian cells and compares favorably on off-target activity.
Selection: Assess transcript knockdown efficiency and off-target activity in tested mammalian cells.
- 5.Single-AAV and disease-relevant application validation(confirmatory_validation)
This stage validates the delivery advantage conferred by compact size and demonstrates application to MYC silencing in human cancer cells.
Selection: Demonstrate that compact size supports single-AAV delivery and multiplex RNA knockdown in a disease-relevant mammalian context.
Taxonomy & Function
Primary hierarchy
Mechanism Branch
Component: A low-level RNA part used inside a larger architecture that realizes a mechanism.
Techniques
Computational DesignTarget processes
degradationlocalizationrecombinationImplementation Constraints
cofactor dependency: cofactor requirement unknownencoding mode: genetically encodedimplementation constraint: context specific validationimplementation constraint: payload burdenoperating role: regulatorswitch architecture: recruitment
CBS requires the matching EcCas6 or dEcCas6 protein context. Its design depends on balancing processing by EcCas6 with binding by EcCas6 and dEcCas6.; requires compatibility with EcCas6 or dEcCas6; used as a stem-loop RNA element in the STAR architecture
Independent follow-up evidence is still limited. Validation breadth across biological contexts is still narrow. Independent reuse still looks limited, so the evidence base may be fragile. No canonical validation observations are stored yet, so context-specific performance remains under-specified.
Validation
Cell-freeBacteriaMammalianMouseHumanTherapeuticIndep. Replication
Supporting Sources
Ranked Claims
STAR can effectively silence the oncogenic RNA MYC in human cancer cells.
including effective silencing of the oncogenic RNA MYC in human cancer cells
The small size of STAR enables delivery via a single AAV and facilitates multiplex RNA knockdown.
the small size of STAR enables delivery via a single adeno-associated virus (AAV) for ease of multiplex RNA knockdown
CBS can be fine-tuned for EcCas6 processing while maintaining conserved binding to EcCas6 and dEcCas6, supporting CBS guide design for recruitment of dEcCas6-toxins.
CBS can be fine-tuned for EcCas6 processing but exhibits high conservatism in EcCas6 and dEcCas6 binding, laying a foundation for the design of CBS guides to effectively recruit dEcCas6-toxins
STAR mediates high-efficiency knockdown of both cytoplasmic and nuclear transcripts in tested mammalian cells.
STAR exhibits high-efficiency knockdown of both cytoplasmic and nuclear transcripts in the tested mammalian cells
STAR has significantly reduced off-target activities compared with established CRISPR and RNA interference technologies.
with significantly reduced off-target activities compared to established CRISPR and RNA interference (RNAi) technologies
STAR is a hypercompact transcript degrader created by integrating engineered small toxin endoribonucleases with dEcCas6 and a CBS RNA element.
integrate catalytically dead Cas6 (dCas6) along with its cognate stem-loop RNA (Cas6 binding site, termed CBS) from Escherichia coli (E. coli) to create hypercompact transcript degraders (317 ~ 430 amino acids), named STAR
protein size range 317~430 amino acids
Approval Evidence
1 source2 linked approval claimsfirst-pass slug cas6-binding-site
its cognate stem-loop RNA (Cas6 binding site, termed CBS)
Source:
mechanistic propertysupports
CBS can be fine-tuned for EcCas6 processing while maintaining conserved binding to EcCas6 and dEcCas6, supporting CBS guide design for recruitment of dEcCas6-toxins.
CBS can be fine-tuned for EcCas6 processing but exhibits high conservatism in EcCas6 and dEcCas6 binding, laying a foundation for the design of CBS guides to effectively recruit dEcCas6-toxins
Source:
tool constructionsupports
STAR is a hypercompact transcript degrader created by integrating engineered small toxin endoribonucleases with dEcCas6 and a CBS RNA element.
integrate catalytically dead Cas6 (dCas6) along with its cognate stem-loop RNA (Cas6 binding site, termed CBS) from Escherichia coli (E. coli) to create hypercompact transcript degraders (317 ~ 430 amino acids), named STAR
Source:
Comparisons
Source-backed strengths
can be fine-tuned for EcCas6 processing; reported to retain high conservatism in EcCas6 and dEcCas6 binding
Source:
can be fine-tuned for EcCas6 processing
Source:
reported to retain high conservatism in EcCas6 and dEcCas6 binding
Compared with MALAT1
Cas6 binding site and MALAT1 address a similar problem space because they share degradation, recombination.
Shared frame: same top-level item type; shared target processes: degradation, recombination; shared mechanisms: degradation
Compared with prime-editing
Cas6 binding site and prime-editing address a similar problem space because they share degradation, localization, recombination.
Shared frame: shared target processes: degradation, localization, recombination; shared mechanisms: degradation
Strengths here: looks easier to implement in practice; may avoid an exogenous cofactor requirement.
Relative tradeoffs: appears more independently replicated.
Compared with synthetically engineered guide RNA
Cas6 binding site and synthetically engineered guide RNA address a similar problem space because they share degradation, recombination.
Shared frame: same top-level item type; shared target processes: degradation, recombination; shared mechanisms: degradation
Ranked Citations
- 1.