Ribosomal Protein Gene Cluster Research Articles

Cluster of ribosomal protein genes in Escherichia coli containing genes for proteins S6, S18, and L9.

A mutant of Escherichia coli K-12 isolated for temperature-sensitive growth was found to harbor an alteration in robosomal protein L9. Because the chromosomal location of the structural gene for this protein (rplI) was not known, we mapped the mutation by using various Hfr strains. The fine mapping of this gene by Plkc phage-mediated transductions has revealed that it forms a gene cluster at 94 min on the E. coli genetic map together with the genes coding for two other ribosomal proteins, S6 (rpsF) and S18 (rpsR). Furthermore, the region of the E. coli genetic map containing this cluster was found to be shorter than previously estimated by approximately 2 min.

New cluster of ribosomal genes in Bacillus subtilis with regulatory role in sporulation

STUDIES of the onset of sporulation in Bacillus subtilis can provide information of value to the study of differentiation in general. Little is known about the molecular mechanisms involved in initiating sporulation, or any other developmental process. Mutations at any one of nine distinct genetic loci may block sporulation in B. subtilis at early stages without affecting vegetative growth1,2. These mutations are pleiotropic, in that they are not only blocked in sporulation but are also impaired, to various degrees, in stage 0 functions such as antibiotic and protease production, competence for transformation, and sensitivity to surface active antibiotics and phage3. We have examined the ribosomal composition of these stage 0 mutants and of the same mutants bearing an additional mutation in another locus, abrB, that results in suppression of the pleiotropic mutant phenotype without suppressing the sporulation defect. We report here that abrB mutations define a new cluster of ribosomal protein genes, with the origin proximal to the main group of ribosomal genes. These findings demonstrate the involvement of ribosomes in the control of early stages of the sporulation cycle.

Genes encoding ribosomal proteins S16 and L19 form a gene cluster at 56.4 min in Escherichia coli

A mutant of Escherichia coli which was isolated for temperature-sensitive growth was found to harbour a structural alterations in protein S16 (Isolo et al., 1978). The mutation was localized by matings with various Hfr strains and by Plkc-mediated transduction. The results showed that it mapped very close to the gene coding for L19 protein which has been placed at 56.4 min (Kitakawa and Isono, 1977), indicating that it most likely forms a new ribosomal protein-gene cluster.

Ribosomal assembly deficiency in an Escherichia coli thermosensitive mutant having an altered L24 ribosomal protein

Localized P1 mutagenesis was used to screen for conditionally lethal mutations in ribosomal protein genes. One such mutation, 2859mis, has been mapped inside the ribosomal protein gene cluster at 72 minutes on the Escherichia coli chromosome and cotransduces at 98% with rpsE (S5). The 2869mis mutation leads to thermosensitivity and impaired assembly in vivo of 50 S ribosomal particles at 42 °C. The strain carrying the mutation has an altered L24 ribosomal protein which at 42 °C shows weaker affinity for 23 S RNA than the wild-type protein. The mutational alteration involves a replacement of glycine by aspartic acid in protein L24 from the mutant. We conclude therefore that the 2859mis mutation affects the structural gene for protein L24 ( rplX).

Transcription patterns of adjacent segments on the chromosome of Escherichia coli containing genes coding for four 50 S ribosomal proteins and the β and β′ subunits of RNA polymerase

The transcription of four distinct segments of the bacterial chromosome has been examined under different conditions of steady-state growth using specific RNA-DNA hybridization assays. The genome segments contain, respectively: (1) a cluster of genes coding for four ribosomal proteins, (2) the gene coding for the β subunit of RNA polymerase, (3) the gene coding for the β′ subunit of RNA polymerase and (4) a cluster of genes coding for 15 ribosomal proteins and the α subunit of RNA polymerase. The first three segments are contiguous and located near 88 minutes, whereas the fourth segment is distinctly separate and located near 72 minutes on the Escherichia coli linkage map. The amount of RNA (measured as a fraction of the total cellular RNA) which hybridized to the DNA segments coding for ribosomal proteins was found to increase with the steady-state growth rate of the bacterium. In contrast, the amount of RNA that was homologous to the genes coding for the β and β′ subunits of RNA polymerase was invariant with the growth rate. The amount of β′ messenger RNA was apparently greater than the amount of β mRNA, suggesting that β′ mRNA is more stable than β mRNA during the exponential phase growth. The amount and frequency of transcription of these DNA segments was determined by hybridization with pulse-labeled RNA. The results of these experiments surprisingly indicated that the four segments were transcribed proportionately and independent of the bacterial growth rate. The ribosomal protein gene clusters at 88 minutes and 72 minutes were transcribed with about equal frequency; this indicates that the transcription of distinctly separate gene clusters can be regulated co-ordinately. The DNA segments coding for the β and β′ subunits of RNA polymerase were transcribed with equal frequency, and their transcription was co-ordinate with, but only one-fourth or one-fifth as frequent as transcription of the adjacent ribosomal protein genes. This observation is consistent with the idea that the genes coding for the β and β′ subunits are cotranscribed, and further suggests that regulation of the β and β′ subunit genes is intimately related to the regulation of the adjacent ribosomal protein genes.

Alteration of ribosomal protein S17 by mutation linked to neamine resistance in Escherichia coli: I. General properties of neaA mutants

A mutant of Escherichia coli strain K12S isolated after selection for resistance to the amino glycoside antibiotic neamine shows severe restriction of amber suppressors in vivo . Ribosomes from the mutant exhibit low neamine-induced misreading in vitro and a decreased affinity for the related antibiotic streptomycin. The S17 ribosomal protein from the mutant strain shows altered electrophoretic mobility on two-dimensional polyacrylamide gels and also differs in chromatographical behaviour from the S17 protein from the parental strain. When ribosomes from the mutant strain are reconstituted in the presence of a molar excess of the S17 protein from the wild type species, the particles exhibit normal druginduced misreading properties as well as a normal capacity for binding streptomycin. The gene involved in the alteration of protein S17 ( rpxQ ) is located inside the ribosomal protein gene cluster at 64 minutes on the E. coli genetic map and cotransduces at 96% with rpxE (S5).

IS1 and IS2 mutations in the ribosomal protein genes of E. coli K-12.

The insertion mutations I15 and I16 in the ribosomal protein gene cluster at 64 min in Escherichia coli are identified as IS1 and IS2 using electron microscope heteroduplex analysis.