CGAS/DncV-like nucleotidyltransferase (CD-NTase) family members are immune sensors that synthesize diverse nucleotide signals to initiate antiviral response in bacteria and animals. As a founding member of CD-NTase enzyme, cGAS has been identified as a key sensor for cytoplasmic DNA and type I interferons (IFNs) signaling in metazoan. However, the functions of other metazoan CD-NTases remain enigmatic. Here, we showed that Mab-21 domain-containing protein 2 (MB21D2), another member of the CD-NTase family, plays a positive role in modulating the cGAS-STING signaling in myeloid cells. Deficiency of MB21D2 in THP-1 cells or mice macrophages led to impaired production of type I interferon upon DNA stimulation. Consistently, Mb21d2^−/− mice showed more susceptible to infection with DNA virus and faster growth of melanoma, compared to its counterparts. Mechanistically, MB21D2 specially bound with the N-terminal of cGAS, facilitated its liquid phase condensation and DNA-binding activity, leading to the enhanced production of cGAMP and subsequent IFN-β production. Thus, our findings unveiled that the CD-NTase family member MB21D2 contributes to host antiviral and antitumor responses by enhancing cGAS activation.

Yeast peroxisomes have been engineered as ideal synthetic compartments to enhance the heterologous biosynthesis of natural products, particularly terpenoids and fatty acid derivatives. This advantage is primarily attributed to the rich acetyl-CoA pool generated from the spatially specific fatty acid β-oxidation within peroxisomes. However, their potential for flavonoid biosynthesis has been largely underexplored, primarily due to limited knowledge regarding precursor transport, cofactor availability, and the redox environment in peroxisomes. In this study, we successfully compartmentalized the biosynthesis of taxifolin, a dihydroflavonol, in Saccharomyces cerevisiae peroxisomes. The result indicated that flavonoid biosynthesis in peroxisome offers a more efficient approach compared to its synthesis in the cytosol. This study managed to expand the application scope of peroxisome compartmentalization to flavonoid biosynthesis. By reinforcing the rate-limiting steps, optimizing cofactor supply and activation of fatty acids, we accomplished the de novo synthesis of taxifolin in peroxisomes for the first time, attaining a titer of 120.3 ± 2.4 mg/L in shake-flask fermentation using a minimal medium. These findings highlight the feasibility of peroxisomal compartmentalization for flavonoid biosynthesis, providing new insights and a framework for the biosynthesis of other high-value flavonoids using yeast peroxisomes.