Near-UV stress in Salmonella typhimurium: 4-thiouridine in tRNA, ppGpp, and ApppGpp as components of an adaptive response.
We have examined the role of 4-thiouridine in the responses of Salmonella typhimurium to near-UV irradiation. Mutants lacking 4-thiouridine (nuv) and mutants defective in the synthesis of ppGpp (guanosine 5'-diphosphate-3'-diphosphate) (relA) were found to be sensitive to killing by near-UV. Near-UV induced the synthesis of a set of proteins that were not induced in the nuv mutant. Some of these proteins were identified as oxidative defense proteins, and others were identified as ppGpp-inducible proteins. Over 100-fold increases in ApppGpp (adenosine 5', 5"'-triphosphoguanosine-3"'-diphosphate, the adenylylated form of ppGpp) were observed in wild-type cells after near-UV irradiation but not in the 4-thiouridine-deficient mutant. These data support a model in which ppGpp and ApppGpp, a dinucleotide proposed to be synthesized by tRNA-aminoacyl synthetases as a response to the cross-linking of 4-thiouridine in tRNA by near-UV, induce the synthesis of proteins necessary for resistance to near-UV irradiation.
Kramer
G F
GF
Department of Biochemistry, University of California, Berkeley 94720.
Baker
J C
JC
Ames
B N
BN
D001426:Bacterial Proteins / Q000096:biosynthesis; D002851:Chromatography, High Pressure Liquid; D005798:Genes, Bacterial; D006150:Guanine Nucleotides / Q000096:biosynthesis*; D006159:Guanosine Tetraphosphate / Q000031:analogs & derivatives / Q000096:biosynthesis* / Q000235:genetics; D009154:Mutation; D012343:RNA, Transfer / Q000378:metabolism; D012486:Salmonella typhimurium / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D013891:Thiouridine / Q000378:metabolism*; D014466:Ultraviolet Rays
D001426:Bacterial Proteins; D006150:Guanine Nucleotides; D013891:Thiouridine; D006159:Guanosine Tetraphosphate; C055772:adenosine 5',5'''-triphosphoguanosine-3'''-diphosphate; D012343:RNA, Transfer