Regulation of the tRNA(5)(Leu)-encoding gene leuX that is associated with a pathogenicity island in the uropathogenic Escherichia coli strain 536

Pathogenicity islands (PAIs) contain virulence determinants and are often l inked to tRNA loci. The leuX gene encoding tRNA(5)(Leu) is associated with PAI II536 of the uropathogenic E. coli strain 536 (O6:K15:H31) and is impor tant for the expression of virulence factors in this strain. Transcription of leuX differs from that of the majority of tRNA genes including the major leucyl-tRNA gene leuV. Availability of the tRNA(5)(Leu) can be linked with the efficient expression of virulence determinants. Transcription of leuX and leuV was studied to gain further insights into the regulation of this t RNA gene and its role during the expression of virulence determinants. leuX but not leuV transcripts accumulated in stationary phase. While leuX trans cription was unchanged or slightly up-regulated by an increase in growth te mperature, osmolarity or ethanol concentration, that of leuV was reduced. T he heat shock-specific sigma factor RpoH was shown to affect transcription of leuX but not of leuV. These results demonstrate that transcription of a tRNA gene can be specifically influenced by an alternative sigma factor. Ou r finding expands our knowledge of the regulation of tRNA gene transcriptio n and represents an additional mode of regulation of gene expression that c an also affect bacterial virulence.