Bacterial DNA methylases as novel molecular and synthetic biology tools: recent developments

Bacterial DNA methylases are a diverse group of enzymes which have been pivotal in the development of technologies with applications including genetic engineering, bacteriology, biotechnology and agriculture. This review describes bacterial DNA methylase types, the main technologies for targeted methylation or demethylation and the recent roles of these enzymes in molecular and synthetic biology. Bacterial methylases can be exocyclic or endocyclic and can exist as orphan enzymes or as a part of the restriction-modifications (R-M) systems. As a group, they display a rich diversity of sequence-specificity. Additional technologies for targeting methylation involve using fusion proteins combining a methylase and a DNA-binding protein (DNBP) such as a zinc-finger (ZF), transcription activator-like effector (TALE) or CRISPR/dCas9. Bacterial methylases have contributed significantly to the creation of novel DNA assembly techniques, to the improvement of bacterial transformation and to crop plant engineering. Future studies to define the characteristics of more bacterial methylases have potential to identify new tools of value in synthetic and molecular biology and with widespread applications. KEY POINTS: • Bacterial methylases can be used to direct methylation to specific sequences in target DNA • DNA methylation using bacterial methylases has been applied to improve DNA assembly and to increase the efficiency of bacterial transformation • Site-selective methylation using bacterial methylases can alter plant gene expression and phenotype.