Published on March 1, 2011 in Nucleic Acids Res volume 39.
PubMed ID: 21097467
Pseudouridine at position 55 (Psi55) in eubacterial tRNA is produced by TruB. To clarify the role of the Psi55 modification, we constructed a truB gene disruptant (DeltatruB) strain of Thermus thermophilus which is an extreme-thermophilic eubacterium. Unexpectedly, the DeltatruB strain exhibited severe growth retardation at 50 degrees C. We assumed that these phenomena might be caused by lack of RNA chaperone activity of TruB, which was previously hypothetically proposed by others. To confirm this idea, we replaced the truB gene in the genome with mutant genes, which express TruB proteins with very weak or no enzymatic activity. However the growth retardation at 50 degrees C was not rescued by these mutant proteins. Nucleoside analysis revealed that Gm18, m(5)s(2)U54 and m(1)A58 in tRNA from the DeltatruB strain were abnormally increased. An in vitro assay using purified tRNA modification enzymes demonstrated that the Psi55 modification has a negative effect on Gm18 formation by TrmH. These experimental results show that the Psi55 modification is required for low-temperature adaptation to control other modified. (35)S-Met incorporation analysis showed that the protein synthesis activity of the DeltatruB strain was inferior to that of the wild-type strain and that the cold-shock proteins were absence in the DeltatruB cells at 50 degrees C.