Functional defects in transfer RNAs lead to the accumulation of ribosomal RNA precursors

Microarray and Northern blot analysis. (A) Visualization of the microarray results corresponding to the serV/argV region. Three independent analyses of total RNA are shown from HMSdrp (drp1, drp2, and drp3) and from a control strain containing a disruption in lacZ (lacZ1, lacZ2, and lacZ3), and one analysis of RNA from HMS174(DE3). The levels of downregulation of the genes and intergenic regions within and abutting the serV/argV region (IG1757 to alaS) are shown on a log₂ scale using a gray-scale shading scheme: (black) no change in mRNA expression; (white) a 256-fold (log₂ = −8) downregulation of gene expression. (B) Schematic of the argVYZQ operon. This operon comprises the serV tRNA gene followed by four identical genes (argV, argY, argZ, and argQ) encoding tRNA^Arg2. A chromosomal deletion between argV and argQ, as depicted, results in the loss of three of these tRNA genes in HMSdrp. (C) Northern blot analysis. RNA samples derived from HMS and HMSdrp were analyzed using oligonucleotide probe #7, complementary to tRNA^Arg2. To correct for differences in RNA loading, the blot was also probed with an oligonucleotide complementary to 5S rRNA (probe #8).