Unhealthy diets rich in fats and/or sugar are considered as the major external cause of the obesity epidemic, which is often accompanied by a significant decrease in gut hormone glucagon-like peptide-1 (GLP1) levels. Numerous studies have demonstrated notable contributions of the gut microbiota in this process. Nevertheless, the underlying mechanism still needs further investigation. The role of epigenetic modifications in gene expression and metabolism has been well demonstrated, with m6A methylation on RNAs being the most prevalent modification throughout their metabolism. In the present study, we found that the expressions of small intestinal Gcg and Pc3, two key genes regulating GLP1 expression, were significantly downregulated in obese mice, associated with reduced GLP1 level. Immunohistochemistry analysis indicated that a high-fat diet slightly increased the density of enteroendocrine L cells in the small intestine, implying that decreased GLP1 levels were not caused by the changes in L cell intensity. Instead, the small intestinal m6A level as well as the expression of known “writers”, mettl3/14 and wtap, were found to be positively correlated with the expression of Gcg and Pc3. Fecal microbiota transplantation with feces from normal and obese mice daily to antibiotic-treated mice revealed that dysbiosis in diet-induced obesity was sufficient to reduce serum GLP1, small intestinal m6A level, and intestinal expressions of Gcg, Pc3, and writer genes (mettl3/14, wtap). However, as the most direct and universal methyl donor, the production of fecal S-adenosylmethionine was neither affected by the different dietary patterns nor their shaped microbiota. These results suggested that microbial modulation of the epitranscriptome may be involved in regulating GLP1 expression, and highlighted epitranscriptomic modifications as an additional level of interaction between diet and individual health.

In bacteriophage T7, the primase synthesizes primer at a specific site, 5′-(G/T)₂GTC-3′. However, the pentanucleotide alone cannot define the activity of the primase. In this study, we demonstrated that the 10-nt sequence flanking the 3′ end of pentanucleotide sites made considerable contributions to the interactions between T7 primase and single-strand DNA (ssDNA). Approximately 26 template sequences with multiple features were screened out from the T7 genome, which exhibited strong binding affinity to T7 primase and high priming activity, thus supporting genome replication. Notably, a dinucleotide in the 3′ flank of the pentanucleotide site was found to be instrumental in T7 primase binding to ssDNA, which might be recognized by the zinc-binding domain of T7 primase. As a result, a multiple-site recognition model for T7 primase to select priming sites was proposed. These results shed light on how T7 primase selects priming sites, a process that may be shared by its bacterial counterparts. Furthermore, our study provides novel methodologies for investigating the interactions between prokaryotic primases and their ssDNA templates, thereby laying the groundwork for the development of novel inhibitors.