Engineering APOBEC3A deaminase for highly accurate and efficient base editing.

Cytosine base editors (CBEs) are effective tools for introducing C-to-T base conversions, but their clinical applications are limited by off-target and bystander effects. Through structure-guided engineering of human APOBEC3A (A3A) deaminase, we developed highly accurate A3A-CBE (haA3A-CBE) variants that efficiently generate C-to-T conversion with a narrow editing window and near-background level of DNA and RNA off-target activity, irrespective of methylation status and sequence context. The engineered deaminase domains are compatible with PAM-relaxed SpCas9-NG variant, enabling accurate correction of pathogenic mutations in homopolymeric cytosine sites through flexible positioning of the single-guide RNAs. Dual adeno-associated virus delivery of one haA3A-CBE variant to a mouse model of tyrosinemia induced up to 58.1% editing in liver tissues with minimal bystander editing, which was further reduced through single dose of lipid nanoparticle-based messenger RNA delivery of haA3A-CBEs. These results highlight the tremendous promise of haA3A-CBEs for precise genome editing to treat human diseases.

Isobutyric acid promotes colorectal cancer metastasis through activating RACK1.

Colorectal cancer (CRC) metastasis plays a crucial role in disease progression, yet the regulatory mechanisms underlying metastasis remain incompletely understood. Isobutyric acid (IBA), a short-chain fatty acid found at high levels in serum of CRC patients, has been shown to be a critical metabolite influencing CRC proliferation. However, its role in tumor metastasis remains unknown. Here, utilizing liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis, we found that levels of IBA were significantly higher in patients with distant organ metastasis of CRC than in those without. Furthermore, IBA promoted CRC metastasis both in vitro and in vivo. Mass spectrometry, immunofluorescence, and cellular thermal shift assay revealed that IBA interacts with RACK1. Mechanistically, IBA binding to and activating RACK1 promotes regulation of downstream Akt and FAK signaling and CRC metastasis. Collectively, our study highlights the critical interplay between IBA and RACK1 and its impact on tumor metastasis. This study suggests that targeting the IBA-RACK1 signaling axis may be an effective therapeutic strategy for controlling CRC metastasis.