DNA microarray analysis of natural killer cell-type lymphoproliferative disease of granular lymphocytes with purified CD3-CD56+ fractions

Natural killer (NK) cell-type lymphoproliferative disease of granular lymphocytes (LDGL) is characterized by the outgrowth of CD3(-)CD16/56(+) NK cells, and can be further subdivided into two distinct categories: aggressive NK cell leukemia (ANKL) and chronic NK lymphocytosis (CNKL). To gain insights into the pathophysiology of NK cell-type LDGL, we here purified CD3(-)CD56(+) fractions from healthy individuals (n=9) and those with CNKL (n=9) or ANKL (n=1), and compared the expression profiles of >12 000 genes. A total of 15 'LDGL-associated genes' were identified, and a correspondence analysis on such genes could clearly indicate that LDGL samples share a 'molecular signature' distinct from that of normal NK cells. With a newly invented class prediction algorithm, 'weighted distance method', all 19 samples received a clinically matched diagnosis, and, furthermore, a detailed cross-validation trial for the prediction of normal or CNKL status could achieve a high accuracy (77.8%). By applying another statistical approach, we could extract other sets of genes, expression of which was specific to either normal or LDGL NK cells. Together with sophisticated statistical methods, gene expression profiling of a background-matched NK cell fraction thus provides us a wealth of information for the LDGL condition.

DNA microarray analysis of hematopoietic stem cell-like fractions from individuals with the M2 subtype of acute myeloid leukemia

Acute myeloid leukemia (AML) may develop de novo or secondarily to myelodysplastic syndrome (MDS). Although the clinical outcome of MDS-related AML is worse than that of de novo AML, it is not easy to differentiate between these two clinical courses without a record of prior MDS. Large-scale profiling of gene expression by DNA microarray analysis is a promising approach with which to identify molecular markers specific to de novo or MDS-related AML. This approach has now been adopted with AC133-positive hematopoietic stem cell-like fractions purified from 10 individuals, each with either de novo or MDS-related AML of the M2 subtype. Sets of genes whose activity was associated with either disease course were identified. Furthermore, on the basis of the expression profiles of these genes, it was possible to predict correctly the clinical diagnosis for 17 (85%) of the 20 cases in a cross-validation trial. Similarly, different sets of genes were identified whose expression level was associated with clinical outcome after induction chemotherapy. These data suggest that, at least in terms of gene expression profiles, de novo AML and MDS-related AML are distinct clinical entities.

Peroxisome proliferator-activated receptor gamma activators inhibit cardiac hypertrophy in cardiac myocytes

BACKGROUND

Peroxisome proliferator-activated receptors (PPARs) are transcription factors belonging to the nuclear receptor superfamily. PPARgamma mRNA is present in cardiac myocytes; however, whether PPARgamma affects cardiac hypertrophy remains unknown.

METHODS AND RESULTS

We investigated the effects of PPARgamma activators on cardiac hypertrophy in neonatal rat cardiac myocytes. Cyclic 4% biaxial mechanical strain caused enlargement of cardiac myocytes (1.3-fold versus control, P<0.0001), but the PPARgamma activators troglitazone and 15-deoxy-Delta(12-14)-prostaglandin J(2) (15d-PGJ(2)) (10 micromol/L) inhibited this effect (troglitazone, -72%, P<0.0005; 15d-PGJ(2), -88%, P<0.0002). Total cell protein was increased by mechanical strain (control, 164.3 microgram/dish; strain, 265.5, P<0.0002), and this effect was inhibited by troglitazone and 15d-PGJ(2) (troglitazone, -61%, P<0.005; 15d-PGJ(2), -72%, P<0.001). [(3)H]Leucine uptake was also increased by mechanical strain (1.9-fold versus control, P<0.002), and this increase was inhibited by troglitazone and 15d-PGJ(2) (troglitazone, -52% at 10 micromol/L, P<0.01; 15d-PGJ(2), -70% at 10 micromol/L, P<0.005). An increase in [(3)H]leucine uptake induced by angiotensin II or phenylephrine was significantly inhibited by troglitazone and 15d-PGJ(2). Mechanical strain induced mRNA expression for brain natriuretic peptide, but PPARgamma activators inhibited this induction. Furthermore, PPARgamma activators inhibited mechanically induced activation of nuclear factor (NF)-kappaB. Pyrrolidine dithiocarbamate, an inhibitor of NF-kappaB activation, inhibited strain-induced [(3)H]leucine uptake (-50% at 100 micromol/L, P<0.05).

CONCLUSIONS

These results demonstrate that PPARgamma activators inhibit cardiac hypertrophy in cardiac myocytes and suggest that PPARgamma activators may regulate cardiomyocyte hypertrophy at least partially through the NF-kappaB pathway.

In vitro reconstitution of the end replication problem

The end replication problem hypothesis proposes that the ends of linear DNA cannot be replicated completely during lagging strand DNA synthesis. Although the idea has been widely accepted for explaining telomere attrition during cell proliferation, it has never been directly demonstrated. In order to take a biochemical approach to understand how linear DNA ends are replicated, we have established a novel in vitro linear simian virus 40 DNA replication system. In this system, terminally biotin-labeled linear DNAs are conjugated to avidin-coated beads and subjected to replication reactions. Linear DNA was efficiently replicated under optimized conditions, and replication products that had replicated using the original DNA templates were specifically analyzed by purifying bead-bound replication products. By exploiting this system, we showed that while the leading strand is completely synthesized to the end, lagging strand synthesis is gradually halted in the terminal approximately 500-bp region, leaving 3' overhangs. This result is consistent with observations in telomerase-negative mammalian cells and formally demonstrates the end replication problem. This study provides a basis for studying the details of telomere replication.

Torsades de pointes ventricular tachycardia induced by mosapride and flecainide in the presence of hypokalemia

We report a 68-year-old man who developed torsades de pointes ventricular tachycardia induced by combined use of mosapride and flecainide. He had a permanent pacemaker (DDD mode) implanted because of sick sinus syndrome (bradytachy syndrome) 6 years earlier. The patient had started taking mosapride for upper abdominal discomfort 2 weeks earlier. On admission, ECG showed prolongation of the QTc interval from 0.48 to 0.56 seconds and self-terminating torsades de pointes occurred. We considered that this proarrhythmia was induced by mosapride in combination with antiarrhythmic agents.

Amlodipine increases nitric oxide synthesis in cytokine-stimulated cultured vascualar smooth muscle cells

OBJECTIVE

If calcium channel blockers affect nitric oxide synthesis in the vascular tissue, they could influence disease progression in coronary arteries. We investigated the effects of the calcium channel blocker amlodipine on nitric oxide synthesis by measuring the production of nitrite, a stable metabolite of nitric oxide, in vascular smooth muscle cells.

METHODS

We measured the production of nitrate in cultured rat vascular smooth muscle cells with the Griess reagent Inducible nitric oxide synthase protein and mRNA expression were assayed by Western blotting and reverse transcription-polymerase chain reaction, respectively. The levels of NF-kappaB proteins in nuclear extracts were analyzed by gel retardation assay.

RESULTS

Incubation of cultures with interleukin-1 , (10 ng/ ml) for 24 h caused a significant increase in nitrite generation. Interleukin-1 l-induced nitrite production by vascular smooth muscle cells was significantly increased by amlodipine in a dose-dependent manner. This augmentative effect of amlodipine was completely abolished in the presence of N(G)-monomethyl-L-arginine or actinomycin D. Amlodipine-induced nitrite production was accompanied by increased inducible nitric oxide synthase mRNA and protein accumulation. Interleukin-1 , induced NF-kappaB activation in vascular smooth muscle cells, and addition of amlodipine further increased this NF-kappaB activation. The effect of amlodipine on nitrite production was maintained in the presence of the calcium channel agonist Bay K 8644.

CONCLUSION

Amlodipine enhances nitric oxide synthesis in cytokine-stimulated cultured vascular smooth muscle cells by L-type calcium channel-independent mechanisms.

Fluvastatin inhibits matrix metalloproteinase-1 expression in human vascular endothelial cells

Matrix metalloproteinase-1 (MMP-1), also called interstitial collagenase, may play an important role in the pathogenesis of atherosclerosis and atherosclerotic plaque rupture. We investigated the effects of fluvastatin on MMP-1 expression in human vascular endothelial cells (ECs). The addition of fluvastatin decreased the basal MMP-1 levels in the culture media of ECs in a time-dependent (0 to 48 hours) and dose-dependent (10(-)(8) to 10(-)(5) mol/L) manner. On the other hand, fluvastatin did not affect tissue inhibitor of metalloproteinase-1 levels. Collagenolytic activity in conditioned media of ECs was also dose-dependently reduced by fluvastatin. The effect of fluvastatin on MMP-1 expression was completely reversed in the presence of mevalonate or geranylgeranyl-pyrophosphate, but not in the presence of squalene. Inhibition of Rho by C3 exoenzyme also significantly decreased MMP-1 expression in ECs. Our findings revealed that fluvastatin decreases MMP-1 expression in human vascular ECs through inhibition of Rho.

Reprimo, a new candidate mediator of the p53-mediated cell cycle arrest at the G2 phase

A novel gene, Reprimo, in which induction in cells exposed to X-irradiation is dependent on p53 expression, has been isolated. Ectopic p53 expression results in the induction of its mRNA. Reprimo is a highly glycosylated protein and, when ectopically expressed, it is localized in the cytoplasm and induces G(2) arrest of the cell cycle. In the arrested cells, both Cdc2 activity and nuclear translocation of cyclin B1 are inhibited, suggesting the involvement of Reprimo in the Cdc2.cyclin B1 regulation pathway. Thus, Reprimo may be a new member involved in the regulation of p53-dependent G(2) arrest of the cell cycle.

Eight UCA codons differentially affect the expression of the lacZ gene in the divE42 mutant of Escherichia coli

In the divE mutant, which has a temperature-sensitive mutation in the tRNA1(Ser) gene, the synthesis of beta-galactosidase is dramatically decreased at the non-permissive temperature. In Escherichia coli, the UCA codon is only recognized by tRNA1(Ser). Several genes containing UCA codons are normally expressed at 42 degrees C in the divE mutant. Therefore, it is unlikely that the defect is due to the general translational deficiency of the mutant tRNA1(Ser). In this study, we constructed mutant lacZ genes, in which one or several UCA codons at eight positions were replaced with other serine codons such as UCU or UCC, and we examined the expression of these mutant genes in the divE mutant. We found that a single UCA codon at position 6 or 462 was sufficient to cause the same level of reduced beta-galactosidase synthesis as that of the wild-type lacZ gene, and that the defect in beta-galactosidase synthesis was accompanied by a low level of lacZ mRNA. It was also found that introduction of an rne-1 pnp-7 double mutation restored the expression of mutant lacZ genes with only UCA codons at position 6 or 462. A polarity suppressor mutation in the rho gene had no effect on the defect in lacZ gene expression in the divE mutant. We propose a model to explain these results.

Noxa, a BH3-only member of the Bcl-2 family and candidate mediator of p53-induced apoptosis

A critical function of tumor suppressor p53 is the induction of apoptosis in cells exposed to noxious stresses. We report a previously unidentified pro-apoptotic gene, Noxa. Expression of Noxa induction in primary mouse cells exposed to x-ray irradiation was dependent on p53. Noxa encodes a Bcl-2 homology 3 (BH3)-only member of the Bcl-2 family of proteins; this member contains the BH3 region but not other BH domains. When ectopically expressed, Noxa underwent BH3 motif-dependent localization to mitochondria and interacted with anti-apoptotic Bcl-2 family members, resulting in the activation of caspase-9. We also demonstrate that blocking the endogenous Noxa induction results in the suppression of apoptosis. Noxa may thus represent a mediator of p53-dependent apoptosis.

Specific radioactivity of europium-152 in roof tiles exposed to atomic bomb radiation in Nagasaki

Specific radioactivities of residual europium (Eu)-152 were measured in six roof tile samples exposed to the Nagasaki atomic bomb at two locations. The ground distances of the two locations from the hypocenter are 1020 m and 1060 m. In order to obtain reliable data, Eu-enriched samples (from 207 to 855 mg) were prepared by separating Eu from each roof tile sample (from 1 to 2 kg). For the major aliquot of the Eu-enriched sample, residual radioactivity of 152Eu was measured using a low-energy photon spectrometer. For the minor aliquot of the Eu-enriched sample, Eu content was determined by neutron activation analysis. Results of the specific radioactivity (152Eu/Eu, Bq mg-1) corrected to the time of bombing were in a range from 0.080 to 0.446. Although the measured values showed some scattering, they are moderately consistent with the calculated values by the DS86 methodology, i.e. the average ratio of the calculated to measured values is 1.3 +/- 0.8.

A whole-genome analysis of allelic changes in renal cell carcinoma by in-gel competitive reassociation

We applied a differential cloning procedure, the in-gel competitive reassociation (IGCR) method, to clone altered genomic sites from the whole genomes of renal cell carcinoma cells. After four rounds of IGCR, we obtained from two patients libraries enriched 1000- and 2500-fold for differential DNA fragments specific to allelic changes in renal cell carcinoma. In these libraries, we found differential fragments of single-copy sequences as well as repetitive sequences. The fragments exhibited allelic loss, restriction-fragment-length polymorphism, size changes, and changes in the copy number, and common allelic losses were also detected in the cancer tissues from several renal cell carcinoma patients. Some of the clones showed changes in the repeat length of microsatellites. One third (seven of 22) of the clones exhibiting these changes were mapped to chromosomes 8 or 9. Decreases in the copy numbers of mitochondrial DNA and satellite I were observed in 13 of 17 and seven of 16 renal cell carcinoma patients, respectively. This suggests that the IGCR method can be used to clone DNA fragments with various structural changes from the whole genomes of cancer tissues.

Conservation and continuity of periodic bent DNA in genomic rearrangements between the c-myc and immunoglobulin heavy chain mu loci

Periodic bent DNA was mapped in the human c- myc and immunoglobulin heavy chain mu (Ig mu) loci. A total of 12 DNA bend sites in the c- myc gene and 11 sites in the Ig mu locus were aligned at average intervals of 694.2 +/- 281.4 and 654.5 +/- 222.7 bp respectively. Although some of the bend sites retained the distance of 700 bp, their periodicity was disturbed at several locations, including the exons of the c- myc gene and the enhancer element present in the Ig mu locus. Analysis of rearrangements that resulted in tumorigenesis of lymphocytes showed that the continuity of DNA bend sites was conserved in three lymphoma cell lines, Manca, BL22 and Ramos, suggesting that the genomic rearrangements gain stability by retaining their periodicity. This adds further evidence that the periodic bent DNA plays a crucial role in genomic structure.

Expression of p53, MDM2 protein and Ki-67 antigen in recurrent meningiomas

Association of p53 gene abnormalities with tumor progression and prognosis of many neoplasms has been demonstrated, but little is known about the clinical significance of p53 abnormalities in meningiomas. The significance of p53 protein expression in recurrent meningiomas and its relationships with MDM2 protein and proliferation activity were investigated by analyzing 39 meningiomas immunohistochemically. p53 protein was expressed in 11 (35%) of 31 non-recurrent and 7 (88%) of 8 recurrent meningiomas. A high frequency of p53 expression was observed in recurrent meningiomas, which tended to have a high p53 positive index (p53 PI), indicating that p53 immunoreactivity may be a marker for predicting tumor recurrence. Four recurrent meningiomas with high p53 PIs were analyzed by the polymerase chain reaction-single strand conformation polymorphism method to detect p53 gene mutations, but none were found in exons 4-8 of this gene. Fifteen (71%) of 21 MDM2-positive and 3 (17%) of 18 MDM2-negative tumors expressed p53 protein, showing that MDM2 expression was more common in meningiomas with p53 expression. p53 immunoreactivity in the absence of mutation may indicate stabilization of the wild type through interaction with the MDM2 protein. The Ki-67/MIB-1 proliferation index (MIB-1 PI) correlated well with recurrence. The p53-positive tumors had a significantly higher mean MIB-1 PI than p53-negative tumors, suggesting that wild-type p53 inactivation by the MDM2 protein may be involved in controlling the proliferative activity in meningiomas. In conclusion, immunohistochemical examination for p53 protein as well as proliferative activity may help predict the malignant potential of tumor recurrence.

An rne-1 pnp-7 double mutation suppresses the temperature-sensitive defect of lacZ gene expression in a divE mutant

A divE mutant, which has a temperature-sensitive mutation in the tRNA1Ser gene, exhibits differential loss of the synthesis of certain proteins, such as beta-galactosidase and succinate dehydrogenase, at nonpermissive temperatures. In Escherichia coli, the UCA codon is recognized only by tRNA1Ser. Several genes containing UCA codons are normally expressed after a temperature shift to 42 degrees C in the divE mutant. Therefore, it is unlikely that the defect in protein synthesis at 42 degrees C is simply caused by a defect in the decoding function of the mutant tRNA1Ser. In this study, we sought to determine the cause of the defect in lacZ gene expression in the divE mutant. It has also been shown that the defect in lacZ gene expression is accompanied by a decrease in the amount of lacZ mRNA. To examine whether inactivation of mRNA degradation pathways restores the defect in lacZ gene expression, we constructed divE mutants containing rne-1, rnb-500, and pnp-7 mutations in various combinations. We found that the defect was almost completely restored by introducing an rne-1 pnp-7 double mutation into the divE mutant. Northern hybridization analysis showed that the rne-1 mutation stabilized lacZ mRNA, whereas the pnp-7 mutation stabilized mutant tRNA1Ser, at 44 degrees C. We present a mechanism that may explain these results.

The structure and organization of the human NPAT gene

Ataxia telangiectasia (AT) is an autosomal recessive gene disorder, and ATM, a housekeeping gene, has been identified as the gene responsible for AT. Recently we found that another housekeeping gene, NPAT, is located upstream of ATM on human chromosome 11. The two housekeeping genes are transcribed in opposite directions and share a 0.5-kb 5' flanking sequence. The structure and organization of NPAT were determined by direct sequencing of cosmid clones carrying the gene and by application of the long and accurate (LA)-PCR method to amplify regions encompassing the exon/intron boundaries and all of the exons. The gene spans at least 44 kb and consists of 18 exons and 17 introns. It has been suggested that AT heterozygotes have an increased risk of developing cancer, especially breast cancer in women. Frequently, loss of heterozygosity at loci on 11q22-q24 has been observed in DNA isolated from tumors of the breast, uterine cervix, and colon, perhaps suggesting the location of a tumor suppressor gene in 11q22-q24. For investigation of the role of NPAT in AT and these tumors with allelic loss of 11q22-q24, appropriate primer sequences and PCR conditions for amplification of all the NPAT exons from genomic DNA were determined. We previously reported that no recombinations are found among Atm, Npat, and Acat1 (acetoacetyl-CoA thiolase) loci as determined by fine genetic linkage mapping of the mouse AT region. The results of the LA-PCR analysis using NPAT- and ACAT-specific primers and human genomic DNA allowed us to map ACAT 12 kb centromeric to NPAT.

bmr3, a third multidrug transporter gene of Bacillus subtilis

A third multidrug transporter gene named bmr3 was cloned from Bacillus subtilis. Although Bmr3 shows relatively low homology to Bmr and Blt, the substrate specificities of these three transporters overlap. Northern hybridization analysis showed that expression of the bmr3 gene was dependent on the growth phase.

Cloning and sequencing of the gene encoding the soluble fumarate reductase from Saccharomyces cerevisiae

A gene of the soluble fumarate reductase (FRDS) that binds FAD non-covalently was cloned by polymerase chain reaction (PCR) using degenerate oligonucleotides designed from partial amino acid sequences of highly purified enzyme. The nucleotide sequence of a 0.99-kb amplified product was found to be nearly identical to a partial sequence of an open reading frame (ORF) previously reported (EMBL database accession number S-30830). According to the sequence in the EMBL database, we cloned 1.7-kb fragment containing entire sequence of this ORF by PCR and found that this fragment contained a perfect match to the 0.99-kb sequence amplified with the degenerate primers. From these results, we concluded that this ORF is the FRDS gene. The amino acid sequences of the regions involved in the non-covalent binding of FAD and the active site, which are conserved among the flavoprotein subunits of membrane-bound fumarate reductase and succinate dehydrogenase, were found in FRDS. However, unlike the membrane-bound enzymes, FRDS did not contain the histidine residue that covalently binds the isoalloxazine ring of FAD at or near the corresponding position. FRDS showed high homology to the product of S. cerevisiae OSM1 gene which was reported to be required for growth in hypertonic media.

Preference of the recombination sites involved in the formation of extrachromosomal copies of the human alphoid Sau3A repeat family

The human alphoid Sau3A repetitive family DNA is one of the DNA species that are actively amplified to form extrachromosomal circular DNA in several cell lines. The circularization takes place between two of the five approximately 170 bp subunits with an average of 73.1% homology as well as between identical subunits. To investigate the nature of the recombination reaction, we cloned and analyzed the subunits containing recombination junctions. Analysis of a total of 68 junctions revealed that recombination had occurred preferentially at four positions 10-25 (A), 40-50 (B), 85-90 (C) and 135-160 (D) in the 170bp subunit structure. Two regions (B and C) were overlapped with the regions with higher homology between subunits, while other two regions (A and D) cannot be explained solely by the regional homology between the subunits. These regions were located at both junctions of the nucleosomal and the linker region, and overlapped with the binding motifs for alpha protein and CENP-B. Approximately 90% of the recombination occurred between the subunits located next but one (+/- 2 shift), although the frequency of recombination between the adjoining subunits (+/- 1 shift) was approximately 10%.

Analysis of recombination junctions in extrachromosomal circular DNA obtained by in-gel competitive reassociation

Essentially all eukaryotic cells contain circular extrachromosomal DNA as a result of excision from the chromosomes. To obtain insight into the nature of recombination associated with the occurrence of such DNA species and its biological significance, we analyzed a library enriched in recombination junctions which was constructed by a novel DNA subtraction technique; in-gel competitive reassociation (IGCR). Furthermore, we also introduced inverse PCR to characterize chromosomal DNA fragments containing the recombination junctions. At least 45% of the clones in the library constructed by the IGCR procedure comprised DNA with recombination junctions. Nucleotide sequence analysis of the recombination junctions indicated that three of four extrachromosomal DNAs thus analyzed were produced through recombination between sequences with a 3-5 bp homology in the chromosomes. One extrachromosomal DNA was apparently generated through non-homologous recombination, possibly by end-to-end joining. These results have demonstrated the usefulness of IGCR in concentrating recombination junctions, which provide the most direct evidence for the mechanism of the recombinational events involved, from highly complex genomes.

A differential cloning procedure for rearranged or altered genomic DNA based on in-gel competitive reassociation

We have developed a substantially improved differential cloning procedure designed for cloning anonymous altered restriction DNA fragments from higher organisms. The improvements include (i) in-gel dissociation and reassociation of biotinylated restriction digests of target DNA fragments, (ii) replacement of agarose gel by a synthetic gel material for electrophoresis, (iii) use of a reassociation enhancing reagent (CTAB) for in-gel reassociation, and (iv) introduction of PCR. After several cycles of IGCR, we attained considerable enrichment of altered or rearranged DNA fragments which were originally present at one copy or less per complex eukaryotic genome. Examples of enrichment include those of an exogenously added DNA fragment, a chromosomal DNA sequence that has undergone a deletion, and DNA fragments containing a recombination junction.

Escherichia coli dnaJ deletion mutation results in loss of stability of a positive regulator, CRP

The dnaJ deletion mutant K7052(lambda dnaK) has a temperature-sensitive defect in the synthesis of beta-galactosidase. We confirmed this operon-specific and temperature-sensitive defect in cell-free extracts prepared from the mutant cells and found that the missing factor was CRP. In the mutant, the cellular concentration of CRP was too low to allow the expression of the lac operon at a nonpermissive temperature. Introduction of a CRP over-producing plasmid into the dnaJ deletion mutant suppressed the defect of beta-galactosidase synthesis. The lower content of CRP in the mutant was found to result from extreme instability of the protein. These results strongly suggested that the heat shock protein dnaJ is involved in the stabilization (or degradation) of CRP.

[Effects on the retina and choroid of transpupillary diode laser photocoagulation]

A transpupillary retinal photocoagulator utilizing GaAlAs diode laser which emits an 810 nm beam has been constructed. It has a continuous-wave mode with a maximum output of 400 mW at the cornea. Animal experiments with monkeys were carried out successfully at various intensities to produce controlled coagulations. Observation by ophthalmoscopy, light and electron microscopes at different time intervals proved diode laser photocoagulation produced more intensive effects in choroid than krypton red laser (647 nm). However, due to the greater absorption of the choroid, there is a tendency to over-coagulation unless conditions are carefully set. No serious side effects in the retina and choroid were observed during the experiments.

A complete deletion mutant of the Escherichia coli dnaKdnaJ operon

Southern hydridization analyses of genomic DNAs from various dnaJ mutants of Escherichia coli showed that mutant K7052, which has well characterized dnaK706 and dnaJ705 double mutantions, is a deletion mutant. The deletion is about 8.0 kb long and encompasses the whole of the dnaKdnaJ operon.

The Escherichia coli dnaJ mutation affects biosynthesis of specific proteins, including those of the lac operon

Temperature-sensitive dnaJ mutants of Escherichia coli showed a thermosensitive defect in the synthesis of beta-galactosidase. Synthesis of the lac mRNA was greatly reduced at the restrictive temperature. The mutants were also conditionally defective in the synthesis of a subset of membrane proteins such as succinate dehydrogenase, whereas the synthesis of anthranilate synthetase, encoded by trpED, as well as that of most cellular proteins, was unaffected at the restrictive temperature. The defect was specific for the dnaJ mutants among several dna mutants which are known to be involved in the initiation of DNA synthesis: dnaK, dnaA, and dnaB mutants synthesized each of these proteins normally even at the restrictive temperature. At the restrictive temperature, growth of the dnaJ mutants was arrested at a specific stage of the cell cycle.