BioTech IP Review

1. Base Editing

Core mechanism:

• Combines a CRISPR-Cas nickase (or dead Cas) with a nucleotide-modifying enzyme, usually a cytidine or adenine deaminase
• Directly converts one base to another without making a double-strand DNA break
• Uses a guide RNA to target a specific DNA sequence

Key outcome:

• Permanent single-nucleotide changes
• Highly precise within a defined “editing window”

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2. Prime Editing

Core mechanism:

• Combines a Cas9 nickase with a reverse transcriptase enzyme
• Uses a prime editing guide RNA (pegRNA) that both specifies the target and encodes the desired edit
• The nickase creates a single-strand nick, then the reverse transcriptase writes the new sequence directly onto DNA

Key outcome:

• Can install insertions, deletions, or substitutions
• No double-strand break required, but more versatile than base editing
• Edits are programmable and longer than a single nucleotide

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3. Epigenetic Editing

Core mechanism:

• Uses a dead Cas (dCas) fused to an epigenetic effector domain
• Effector can add or remove chemical marks (e.g., methylation, acetylation) on DNA or histones
• Guide RNA targets the locus, but the DNA sequence itself is not altered

Key outcome:

• Changes gene expression rather than sequence
• Reversible and tunable
• Useful for regulation-focused therapies or functional studies

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Summary

Feature	Base Editing	Prime Editing	Epigenetic Editing
DNA Break	No	No (single-strand nick)	No
DNA Change	Single base	Substitutions, insertions, deletions	None
Enzyme	Deaminase + Cas nickase	Reverse transcriptase + Cas nickase	Epigenetic effector + dCas
Reversibility	Permanent	Permanent	Often reversible
Complexity	Simple	More complex	Moderate
Therapeutic focus	Monogenic disease	Broader mutation types	Gene regulation / dosage*