Figure 8.

Model of the immune response and Gm18 methylation in tRNA. Transfer RNA from H. influenzae, a respiratory infectious bacterium, induces dimer formation by Toll like receptor-7 (TLR7), the immune response is then stimulated via binding of the proteins, MyD88, IRAK1 and IRAK4. In contrast, human and E. coli tRNAs do not stimulate TLR7 because they contain the Gm18 modification. The E. coli trmH gene disruptant strain does not show any obvious phenotype under laboratory culture conditions [7]. Both Gm18 modification and TrmH are required for survival of E. coli in animal gut.