DNA Methylation by Restriction Modification Systems Affects the Global Transcriptome Profile in Borrelia burgdorferi

Abstract

Prokaryote restriction modification (RM) systems serve to protect bacteria from potentially detrimental foreign DNA. Recent evidence suggests that DNA methylation by the methyltransferase (MTase) components of RM systems can also have effects on transcriptome profiles. The causative agent of Lyme disease, Borrelia burgdorferi, encodes two RM systems with N6-Methyladenosine (m6A) MTase activity. The specific recognition and/or methylation sequences have not been identified for either B. burgdorferi MTase, and it is not currently known whether these RM systems influence transcriptome profiles. In the current study, Single Molecule Real Time sequencing was utilized to map genome-wide m6A sites, and to identify consensus modified motifs in wild-type B. burgdorferi as well as isogenic MTase mutants. Four conserved m6A motifs were identified, and were fully attributable to the presence of specific MTases. Whole-genome transcriptome changes were observed in conjunction with the loss of MTase enzymes, indicating that DNA methylation by RM systems has effects on gene expression in B. burgdorferi. The results of this study provide a comprehensive view of the DNA methylation pattern in B. burgdorferi, and the accompanying gene expression profiles add to the emerging body of research on RM systems and gene regulation in bacteria.\n\nIMPORTANCELyme disease is the most prevalent vector-borne disease in North America, and is classified by the Centers for Disease Control and Prevention (CDC) as an emerging infectious disease with an expanding geographical area of occurrence. Previous studies have shown that the causative bacterium, Borrelia burgdorferi, methylates its genome using restriction modification systems that allow for the distinction of self from foreign DNA. Although much research has focused on the regulation of gene expression in B. burgdorferi, the effects of DNA methylation on gene regulation has not been evaluated. The current study characterizes the patterns of DNA methylation by restriction modification systems in B. burgdorferi, and evaluates the resulting effects on gene regulation in this important pathogen.