Cooperativity between Cas9 and hyperactive AID establishes broad and diversifying mutational footprints in base editors.

The partnership of DNA deaminase enzymes with CRISPR-Cas nucleases is now a well-established method to enable targeted genomic base editing. However, an understanding of how Cas9 and DNA deaminases collaborate to shape base editor (BE) outcomes has been lacking. Here, we support a novel mechanistic model of base editing by deriving a range of hyperactive activation-induced deaminase (AID) base editors (hBEs) and exploiting their characteristic diversifying activity.

CRISPR tiling screen reveals cancer epigenetic 'Goldilocks' state.

CRISPR tiling screens offer an efficient way to identify gain-of-function mutations in targets of cancer therapy. Recently, by utilizing these screens, Kwok et al. unexpectedly discovered mutations conferring drug addiction in lymphoma, revealing a requirement for a 'just right' window of histone methylation crucial for cancer survival.

Structure-Guided Design of a Potent and Specific Inhibitor against the Genomic Mutator APOBEC3A.

Nucleic acid structure plays a critical role in governing the selectivity of DNA- and RNA-modifying enzymes. In the case of the APOBEC3 family of cytidine deaminases, these enzymes catalyze the conversion of cytosine (C) to uracil (U) in single-stranded DNA, primarily in the context of innate immunity. DNA deamination can also have pathological consequences, accelerating the evolution of viral genomes or, when the host genome is targeted by either APOBEC3A (A3A) or APOBEC3B (A3B), promoting tumor evolution leading to worse patient prognosis and chemotherapeutic resistance.

The Base-Editing Enzyme APOBEC3A Catalyzes Cytosine Deamination in RNA with Low Proficiency and High Selectivity.

Human APOBEC3A (A3A) is a nucleic acid-modifying enzyme that belongs to the cytidine deaminase family. Canonically, A3A catalyzes the deamination of cytosine into uracil in single-stranded DNA, an activity that makes A3A both a critical antiviral defense factor and a useful tool for targeted genome editing. However, mutagenesis by A3A has also been readily detected in both cellular DNA and RNA, activities that have been implicated in cancer.

Controllable genome editing with split-engineered base editors.

DNA deaminase enzymes play key roles in immunity and have recently been harnessed for their biotechnological applications. In base editors (BEs), the combination of DNA deaminase mutator activity with CRISPR-Cas localization confers the powerful ability to directly convert one target DNA base into another. While efforts have been made to improve targeting efficiency and precision, all BEs so far use a constitutively active DNA deaminase.