Kawasaki Disease Associated Acute Abdomen: Most Require No Surgery

Objective

To summarize the clinical features and treatment experiences of patients with Kawasaki disease (KD)-associated acute abdomen (KD-AA).

Methods

We conducted a retrospective case-control study of patients with KD-AA treated at our hospital between January 2006 and November 2022.

Results

Of the 917 children with KD, 43 (4.7%) presented with AA. Of these, 33 with complete information were included in the KD-AA group. Patients with KD-AA were significantly older, with higher neutrophil rate, C-reactive protein, procalcitonin, and alanine transaminase levels and lower hemoglobin, albumin, and serum sodium levels. Additionally, more patients with KD-AA presented with aseptic meningitis and KD shock syndrome than those with KD alone (all p<0.05). The two groups did not differ in the incidence of intravenous immunoglobulin (IVIG) resistance, incomplete KD, or coronary artery abnormalities. All patients received aspirin and IVIG therapy, with nine receiving a second dose of IVIG and 11 receiving corticosteroids. Only two patients with KD-AA underwent surgery, and the prognosis of all patients with KD-AA was good.

Conclusion

KD-AA should be suspected in febrile children with abdominal symptoms. Prompt diagnosis of KD-AA is important for early effective treatment to avoid unnecessary surgical harm. KD, complicated by acute abdomen, has a good prognosis.

Clinical Analysis of Acute Suppurative Thyroiditis in 18 Children

Objective

To summarize our clinical experience with the diagnosis and treatment of children with acute suppurative thyroiditis (AST).

Methods

We retrospectively reviewed the clinical data of 18 children with AST treated at our hospital between January 2009 and May 2022.

Results

There were 8 boys and 10 girls, aged 7.8 ± 3.8 years at admission. The main clinical manifestations were fever (88.9%), neck pain (100%), and neck mass (100%). Blood and pus cultures were performed in 9 and 15 patients, respectively. All blood cultures were negative, while positive pus cultures were noted in eight cases (six Streptococcus spp., one Staphylococcus spp., and one Streptococcus spp. and Staphylococcus spp. mixed infection). Additionally, all patients received antibiotic treatment: three received antibiotics alone, seven received antibiotics and ultrasound (US)-guided needle aspiration, seven received antibiotics as well as surgical incision and drainage, and one received antibiotics, US-guided needle aspiration in addition to surgical incision and drainage. Consequently, the average length of hospital stay in patients who received antibiotics and US-guided needle aspiration was 9.1±2.9 days compared to 14.0±2.0 days in patients in the antibiotics alone group and 13.0 ± 2.2 days in patients in the antibiotics and surgical incision and drainage group. Follow-up was conducted in 15 of the 18 patients. Three patients relapsed, and the prognosis of the other patients was good.

Conclusion

AST has atypical clinical symptoms at the early stage. Regular monitoring of the thyroid gland using ultrasonography is strongly advised in unsure cases. Antibiotics combined with US-guided aspiration is a safe, effective, and minimally invasive treatment for AST in children and can reduce hospital stay. However, surgery may be necessary, particularly in the presence of complications. It is strongly recommended that patients with recurrence be examined for anatomical abnormalities and undergo radical treatment.

Effects of PIM3 in prognosis of colon cancer

PURPOSE

PIM kinase is called proto-oncogene, but there are less research on PIM family in colon cancer. This study was designed to explore the prognosis of PIM3 in colon cancer.

METHODS

In this study, we downloaded RNA-seq and clinical information of colon cancer from the Gene Expression Omnibus (GEO) database. Kaplan-Meier method was used for analyzing the impact of PIM3 on the survival of patients with colon cancer. Single-factor and multi-factor cox regression analysis were used for verifying the prognostic value of PIM3. Spearman correlation analysis was used for screening PIM3 related genes. Functional enrichment analysis was used for analyzing the biological functions and pathways in which PIM3 related genes may be involved. STRING online tools were used for building a co-expression network. Cytoscape was used for co-expression network visualization.

RESULTS

Compared with the low expression group, the patients in the PIM3 high expression group lived longer time. Single-factor and multi-factor cox regression analysis indicated that PIM3 was an independent prognostic factor for colon cancer. Sixty-two PIM3 related genes were screened, and GO and KEGG enrichment analyses suggested that PIM3 related genes might be involved in the MAPK and WNT pathways. The co-expression network showed a strong correlation between PIM3 and MLKL, MYL5, PPP3R1 and other genes.

CONCLUSIONS

PIM3 is an independent prognostic factor of colon cancer and may be a target for the diagnosis and treatment of colon cancer.

[Epidemiological characteristics of COVID-19 in Wuchang district of Wuhan]

Objective: To analyzes epidemiological characteristics of COVID-19 and provide evidence for adjustment for COVID-19 prevention and control strategies. Methods: The data of COVID-19 cases in Wuchang district reported as of 19 March, 2020 were obtained from National Notifiable Disease Report System of Chinese Disease Prevention and Control Information System. The software's of Excel 2010, SPSSS 22.0, Arc GIS10.2 and Joinpoint regression program 4.8.0.0 were used for statistical analysis. Results: A total of 7547 COVID-19 cases had been reported as of 19 March, 2020 in Wuchang district, including 5 448 confirmed cases (72.19%), 2009 clinical diagnosed cases (26.62%) and 90 asymptomatic cases case (1.19%). The age of the cases was (56.65±16.25) years and age ranged from 2 days to 105 years among confirmed cases, 2634 were males (48.35%) and 2814 were females (51.65%), 2 492 were retirees (45.74%). A total of 545 health workers were infected with SARS-CoV-2 (7.22% of all cases) including 365 confirmed cases and 5 cases have died. A total of 430 cases of death were reported with case fatality rate of 7.89% (430/5 448), case fatality rate of males (10.9%, 266/2 634) was higher than that of females (5.82%, 164/2 814). The first phase of epidemic peak was from January 24 to January 26, the second phase of epidemic peak was from February 1 to February 5 and there was no one of new confirmed case in one day for the first time on March 18. The first four Streets with the highest incidence rates of confirmed cases were Huanghelou Street (1 043.77/100 000), Ziyang Street (627.97/100 000), Yangyuan Street (503.67/100 000) and Shuiguohu Street (486.02/100 000). Compared with females, aged ≤50 years and mild cases of clinical classification respectively, males (RR=0.690, 95%CI: 0.322-1.478), aged >50 years (RR=11.745, 95%CI: 6.878-20.058), severe cases (RR=2.317, 95%CI: 1.789-3.000) and critical cases of clinical classification (RR=10.794, 95%CI: 7.997-14.569), and gender time-dependent covariate (RR=1.392, 95%CI: 1.053-1.840) were major influencing factors of prognosis of COVID-19 confirmed cases. Conclusions: The gender, ages and occupation of distribution were wide among COVID-19 cases in Wuchang district. Males, aged >50 years, severe cases and critical cases of clinical classification were influencing factors of prognosis of COVID-19 confirmed cases. The standardized management of discharged cases, asymptomatic infected cases and close contact persons were main measures to reduce incidence rates of COVID-19 cases.

The safety and efficacy of endoscopic submucosal dissection for treating early oesophageal carcinoma: a meta-analysis

INTRODUCTION

Oesophageal carcinoma is the sixth most lethal cancer in the world. At present, the choice of specific surgical methods is controversial. This study compares the safety and efficacy of endoscopic submucosal dissection and endoscopic mucosal resection in treating early oesophageal carcinoma.

METHODS

We carried out a search of online databases including the Web of Science, PubMed, Embase and the Cochrane Library with no language restrictions. The inclusion criteria were patients with early oesophageal carcinoma who accepted the treatment of endoscopic submucosal dissection compared with endoscopic mucosal resection.

FINDINGS

A total of 1,462 patients with 1,650 lesions from nine studies were included in the meta-analysis. When compared with the endoscopic mucosal resection group, the en bloc resection (endoscopic submucosal dissection 67.94% vs endoscopic mucosal resection 52.78%; odds ratio 19.79, p = 0.000) and complete resection (endoscopic submucosal dissection 75.57% vs endoscopic mucosal resection 59.47%; odds ratio 16.10, p = 0.000) rates were significantly higher in the endoscopic submucosal dissection group, while the local recurrence rate was significantly lower in the endoscopic submucosal dissection group (endoscopic submucosal dissection 0.08% vs endoscopic mucosal resection 2.66%; odds ratio 0.08, p = 0.000). The incidence of complications and procedural time were also tested.

[Influence of apatinib and VEGFR2-906T>C polymorphism on clinical outcomes of advanced non-small cell lung cancer patients]

Objective: To investigate the clinical outcomes of advanced non-small cell lung cancer (NSCLC) treated by apatinib regimens and the influence of VEGFR2-906T>C polymorphism. Methods: A total of 109 patients with advanced NSCLC who were treated by apatinib after three and more lines from March 2015 to December 2017 in the Department of Oncology of the First Affiliated Hospital of Zhengzhou University were included in this study. Overall response rates were evaluated after 2 cycles, then progression free survival (PFS) and overall survival (OS) were investigated, and safety data were recorded. Additionally, peripheral blood and the biopsy tissue specimens of some NSCLC patients were collected for the genotyping of genetic variation and VEGFR2 gene mRNA expression, respectively. The association between genotype and other characteristics and VEGFR2 gene mRNA expression were analyzed. The univariate analysis of genotypes and prognosis was carried out by Kaplan-Meier survival analysis, and multivariate analysis were adjusted by Cox regression analysis. Results: The treatment effect could be evaluated in all the 109 patients, among them, complete remission (CR) 0 case, partial remission (PR) 19 case, stable disease (SD) 58 case, progression disease (PD) 32 case. Overall response rate (ORR) was 17.43%, disease control rate (DCR) was 70.64%, median PFS was 4.35 months, median OS was 8.35 months. Of the polymorphisms analyzed, only -906T>C was of clinical significance. The prevalence of -906T>C in VEGFR2 among the study population were as follows: TT genotype 64 cases (58.72%), TC genotype 37 cases (33.94%), CC genotype 8 cases (7.34%), minor allele frequency of -906T>C was 0.24. The distribution of three genotypes was in accordance with Hardy-Weinberg Equilibrium (P=0.418). CC and TC genotype patients were merged in the comparison of clinical outcomes. The analysis of patients with different genotypes found that the ORR of CC/TC genotypes and TT genotypes were 13.33% and 20.31% (P=0.377), respectively. And the median PFS of patients with CC/TC genotype and TT genotype were 3.25 and 5.35 months, respectively, which was statistically significant (P=0.007). In terms of OS, the median OS of the two genotypes were 7.35 and 9.15 (P=0.014), respectively. Adjusted in multivariate Cox regression analysis of PFS, TC/CC genotypes were an independent factor for PFS (OR=1.83, P=0.015). The correlation between -906T>C and adverse reactions was not found in the safety analysis. Additionally, of the 69 biopsy tissue specimens, gene expression analysis was conducted. And the results show that the mRNA expression of VEGFR2 in cancer tissues of the patients with CC/TC genotypes were significantly higher than those of the TT genotype patients (P<0.001). Conclusions: Apatinib is safe and effective for patients with advanced non-small cell in multiline therapy. VEGFR2 -906T>C CC/TC genotype has a worse effect on apatinib multiline treatment in patients with advanced NSCLC.

Measurement of density fluctuation propagation direction via the far-forward collective scattering diagnostic based on polarimeter-interferometer

Previously, the 17-channel three-wave polarimeter-interferometer system (POLARIS) on the J-TEXT tokamak has been implemented to measure far-forward collective scattering (FFCS) from electron density fluctuations. Recently, this system has been exploited to measure the propagation direction of density fluctuation. After considering the refraction of the laser probe beam passing through plasma, the ray tracing result shows that the detector of POLARIS may receive asymmetric far-forward scattering beams. Thus, the heterodyne detection of FFCS is available to identify the propagation direction of density fluctuation by resolving the asymmetric scattering spectrum. Experimentally, the transform of the heterodyne scattering spectrum from symmetry to asymmetry has been observed, while the refraction effect becomes strong demonstrating the capacity of measuring the propagation direction of fluctuation. Furthermore, by changing the plasma potential through the use of an applied positive electrode biasing, the reverse of frequency shift for the heterodyne scattering spectrum is identified, confirming the validity of direction discrimination of density fluctuation.

Far-forward collective scattering measurements by FIR polarimeter-interferometer on J-TEXT tokamak

The multi-channel three-wave polarimeter-interferometer system on J-TEXT tokamak has been exploited to measure far-forward collective scattering from electron density fluctuations. The diagnostic utilizes far infrared lasers operated at 432 μm with 17-channel vertical chords (3 cm chord spacing), covering the entire cross section of plasma. Scattering laser power is measured using a high-sensitivity Schottky planar diode mixer which can also detect polarimetric and interferometric phase simultaneously. The system provides a line-integrated measurement of density fluctuations with maximum measurable wave number: k_⊥max ≤ 2 cm^-1 and time response up to 350 kHz. Feasibility of the diagnostic has been tested, showing higher sensitivity to detect fluctuation than interferometric measurement. Capability of providing spatial-resolved information of fluctuation has also been demonstrated in preliminary experimental applications.

High resolution polarimeter-interferometer system for fast equilibrium dynamics and MHD instability studies on Joint-TEXT tokamak (invited)

A high-performance Faraday-effect polarimeter-interferometer system has been developed for the J-TEXT tokamak. This system has time response up to 1 μs, phase resolution < 0.1° and minimum spatial resolution ∼15 mm. High resolution permits investigation of fast equilibrium dynamics as well as magnetic and density perturbations associated with intrinsic Magneto-Hydro-Dynamic (MHD) instabilities and external coil-induced Resonant Magnetic Perturbations (RMP). The 3-wave technique, in which the line-integrated Faraday angle and electron density are measured simultaneously by three laser beams with specific polarizations and frequency offsets, is used. In order to achieve optimum resolution, three frequency-stabilized HCOOH lasers (694 GHz, >35 mW per cavity) and sensitive Planar Schottky Diode mixers are used, providing stable intermediate-frequency signals (0.5-3 MHz) with S/N > 50. The collinear R- and L-wave probe beams, which propagate through the plasma poloidal cross section (a = 0.25-0.27 m) vertically, are expanded using parabolic mirrors to cover the entire plasma column. Sources of systematic errors, e.g., stemming from mechanical vibration, beam non-collinearity, and beam polarization distortion are individually examined and minimized to ensure measurement accuracy. Simultaneous density and Faraday measurements have been successfully achieved for 14 chords. Based on measurements, temporal evolution of safety factor profile, current density profile, and electron density profile are resolved. Core magnetic and density perturbations associated with MHD tearing instabilities are clearly detected. Effects of non-axisymmetric 3D RMP in ohmically heated plasmas are directly observed by polarimetry for the first time.

Microvessel density of hepatocellular carcinoma: its relationship with prognosis

PURPOSE

To elucidate the relationship between angiogenesis and prognosis after curative resection of hepatocellular carcinoma (HCC).

METHODS

An immunohistochemical study using anti-CD34 monoclonal antibody was carried out on surgical specimens from 78 HCC patients who had undergone curative resection; microvessel density (MVD) was counted and the overall survival and disease-free survival were analyzed retrospectively.

RESULTS

Blood vessels in the tumor were strongly stained by anti-CD34 antibody, but not those in the surrounding liver parenchyma. There were three types of tumor vessels: capillary-like (n = 59), sinusoid-like (n = 16) and mixed-type (n = 3). The median MVD count was 100 per field. The HCC were designated as hypovascular (n = 36) with an MVD count below 100, and hypervascular (n = 42) with an MVD count of 100 or more per field. The 5-year survival and disease-free survival rates were 49.7% and 42.8% respectively, and statistical analysis showed that the MVD level was not correlated with tumor size, capsule status, Edmondson's grade, alpha-fetoprotein level, associated cirrhosis, gamma-glutamyltransferase, and serum HBsAg status. The sinusoid-like tumor vessels appeared more frequently in the more differentiated tumors (P<0.05). No statistical difference in overall and disease-free survival between different MVD levels and microvessel types was found. Tumor size was the only predicting factor in the entire series. In patients with small HCC (< or =5 cm, n = 40), 5-year survival and disease-free survival rates were 58.9% and 52.7% respectively, higher than the values in large HCC (39.8% and 32.0% respectively, P<0.05). The MVD level was an independent predicting factor of disease-free survival, 5-year disease-free survival in the hypovascular group (74.6%) being better than that in the hypervascular group (34.7%, P<0.05).

CONCLUSIONS

The MVD level was not related to tumor size, capsule statuo, Edmondson's grade, alpha-fetoprotein level, associated cirrhosis, gamma-glutamyltransferase and serum HBsAg status. In the entire series, tumor size was the only factor influencing survival after curative resection. However, in patients with small HCC, the MVD level was an independent factor of disease-free survival. The pathological and clinical implications of different types of tumor vessels in HCC remain to be studied.

The rpoB mutants destabilizing initiation complexes at stringently controlled promoters behave like "stringent" RNA polymerases in Escherichia coli

In Escherichia coli, stringently controlled genes are highly transcribed during rapid growth, but "turned off" under nutrient limiting conditions, a process called the stringent response. To understand how transcriptional initiation at these promoters is coordinately regulated, we analyzed the interactions between RNA polymerase (RNAP) (both wild type and mutants) and four stringently controlled promoters. Our results show that the interactions between RNAP and stringently controlled promoters are intrinsically unstable and can alternate between relatively stable and metastable states. The mutant RNAPs appear to specifically further weaken interactions with these promoters in vitro and behave like "stringent" RNAPs in the absence of the stringent response in vivo, constituting a novel class of mutant RNAPs. Consistently, these mutant RNAPs also activate the expression of other genes that normally require the response. We propose that the stability of initiation complexes is coupled to the transcription of stringently controlled promoters, and this unique feature coordinates the expression of genes positively and negatively regulated by the stringent response.

Multiple regions on the Escherichia coli heat shock transcription factor sigma32 determine core RNA polymerase binding specificity

We have analyzed the core RNA polymerase (RNAP) binding activity of the purified products of nine defective alleles of the rpoH gene, which encodes sigma32 in Escherichia coli. All mutations studied here lie outside of the putative core RNAP binding regions 2.1 and 2.2. Based on the estimated K(s)s for the mutant sigma and core RNAP interaction determined by in vitro transcription and by glycerol gradient sedimentation, we have divided the mutants into three classes. The class III mutants showed greatly decreased affinity for core RNAP, whereas the class II mutants' effect on core RNAP interaction was only clearly seen in the presence of sigma70 competitor. The class I mutant behaved nearly identically to the wild type in core RNAP binding. Two point mutations in class III altered residues that were distant from one another. One was found in conserved region 4.2, and the other was in a region conserved only among heat shock sigma factors. These data suggest that there is more than one core RNAP binding region in sigma32 and that differences in contact sites probably exist among sigma factors.

RNA polymerase beta mutations have reduced sigma70 synthesis leading to a hyper-temperature-sensitive phenotype of a sigma70 mutant

This work describes a mutational analysis of the interaction between the beta and sigma subunits of Escherichia coli RNA polymerase. The rpoD800 mutant has a temperature-sensitive growth phenotype because the mutant sigma70 polypeptide is not stable at a high temperature. Some rpoB mutations, including rpoB114, enhanced the temperature sensitivity of the rpoD800 mutant. We determined the mechanism by which the rpoB114 rpoD800 double mutant becomes hyper-temperature sensitive for growth. We found that the levels of the mutant sigma70 in the rpoB114 rpoD800 mutant were dramatically reduced compared to that in the rpoD800 mutant after temperature shift-up. The rate of synthesis of the sigma70 polypeptide was reduced in the rpoB114 rpoD800 double mutant compared to the rpoD800 mutant, whereas the half-life of the mutant sigma70 polypeptide after temperature shift-up was the same in both strains. We conclude that because of the reduction of expression of rpoD800 by rpoB114, in concert with the intrinsic instability of the mutant sigma70 polypeptide, the amount of holoenzyme containing sigma70 becomes limiting upon temperature shift-up. This results in the hyper-temperature sensitivity of the rpoB114 rpoD800 double mutant. Furthermore, the effect of rpoB114 on the expression of sigma70 is independent of the rpoD800 allele and is at the transcriptional level. In vitro transcription assays showed that the mutant RNA polymerase RpoB114 was defective in transcribing the two major promoters of the rpoD operon specifically. The effects of these rpoB mutations on gene expression are discussed.

Interaction of Gal repressor with inducer and operator: induction of gal transcription from repressor-bound DNA

Gal repressor inhibits transcription from the gal promoter (P1) when it binds to the cognate operator (O(E)). The repression is relieved by the presence of the inducer D-galactose. Compared with its interaction with free repressor, D-galactose binds to the repressor-operator complex with 10-fold reduced affinity as determined by fluorescence enhancement measurements. Thermodynamic analysis and fluorescence anisotropy showed that the stability of the repressor-operator complex is reduced by only 7-fold by the presence of the inducer in the complex. The formation of the inducer-repressor-operator ternary complex has been confirmed by CD spectral analysis. Fluorescence spectroscopy and energy transfer experiments suggest that individual allosteric effects of the two ligands, inducer and operator, on Gal repressor are responsible for the slightly weakened stability of the ternary complex compared with the stability of the inducer-repressor and repressor-operator complexes. In vitro transcription results demonstrated full derepression of transcription of the P1 promoter under conditions in which the concentrations of the inducer-repressor binary complex are severalfold higher than the dissociation constant of the inducer-repressor-operator ternary complex into inducer-repressor and free DNA. These results strongly suggest that the inducer binding to the repressor-operator complex does not lead to dissociation of the repressor from the operator during transcription induction. Because Gal repressor inhibits transcription by modulating the alpha subunit of the P1-bound RNA polymerase, we conclude that the inducer binding to the operator-bound repressor only allosterically relieves the inhibitory effect of repressor on RNA polymerase without dissociating the repressor from DNA.

The non-inducible nature of super-repressors of the gal operon in Escherichia coli

We isolated and characterized mutant repressors (GalR) of the gal operon in Escherichia coli. These repressors (super-repressors), called GalRs, have a non-inducible phenotype. Repression of the gal operon by super-repressors cannot be lifted by inducer. The mutant galR genes, galRs, have been cloned and the mutational changes determined. Two of them, galRuv7s and galR78s, were located in the proposed sugar binding domains of the repressor. The repressor from wild-type (galR+), as well as from mutant galRuv7s, was purified and characterized biochemically. The results showed that, like wild-type GalR+, GalRuv7s binds to DNA normally and represses transcription from the P1 promoter and stimulates that from the P2 promoter of the gal operon. Nevertheless, compared to GalR+, GalRuv7s is much less sensitive to the presence of the inducer, D-galactose. The affinity of D-galactose to GalRuv7s is 10 to 30-fold lower, as measured by the effect of the inducer on GalR tryptophan fluorescence; GalR complexes with DNA and on GalR repression of transcription. Our results suggest that the super-repressor phenotype of GalRuv7s is because of a defect in D-galactose binding rather than a defect in the ligand-induced allosteric change or increased affinity for the operator.

How a mutation in the gene encoding sigma 70 suppresses the defective heat shock response caused by a mutation in the gene encoding sigma 32

In Escherichia coli, transcription of the heat shock genes is regulated by sigma 32, the alternative sigma factor directing RNA polymerase to heat shock promoters. sigma 32, encoded by rpoH (htpR), is normally present in limiting amounts in cells. Upon temperature upshift, the amount of sigma 32 transiently increases, resulting in the transient increase in transcription of the heat shock genes known as the heat shock response. Strains carrying the rpoH165 nonsense mutation and supC(Ts), a temperature-sensitive suppressor tRNA, do not exhibit a heat shock response. This defect is suppressed by rpoD800, a mutation in the gene encoding sigma 70. We have determined the mechanism of suppression. In contrast to wild-type strains, the level of sigma 32 and the level of transcription of heat shock genes remain relatively constant in an rpoH165 rpoD800 strain after a temperature upshift. Instead, the heat shock response in this strain results from an approximately fivefold decrease in the cellular transcription carried out by the RNA polymerase holoenzyme containing mutant RpoD800 sigma 70 coupled with an overall increase in the translational efficiency of all mRNA species.

A mutant sigma 32 with a small deletion in conserved region 3 of sigma has reduced affinity for core RNA polymerase

sigma 70, encoded by rpoD, is the major sigma factor in Escherichia coli. rpoD285 (rpoD800) is a small deletion mutation in rpoD that confers a temperature-sensitive growth phenotype because the mutant sigma 70 is rapidly degraded at high temperature. Extragenic mutations which reduce the rate of degradation of RpoD285 sigma 70 permit growth at high temperature. One class of such suppressors is located in rpoH, the gene encoding sigma 32, an alternative sigma factor required for transcription of the heat shock genes. One of these, rpoH113, is incompatible with rpoD+. We determined the mechanism of incompatibility. Although RpoH113 sigma 32 continues to be made when wild-type sigma 70 is present, cells show reduced ability to express heat shock genes and to transcribe from heat shock promoters. Glycerol gradient fractionation of sigma 32 into the holoenzyme and free sigma suggests that RpoH113 sigma 32 has a lower binding affinity for core RNA polymerase than does wild-type sigma 32. The presence of wild-type sigma 70 exacerbates this defect. We suggest that the reduced ability of RpoH113 sigma 32 to compete with wild-type sigma 70 for core RNA polymerase explains the incompatibility between rpoH113 and rpoD+. The rpoH113 cells would have reduced amounts of sigma 32 holoenzyme and thus be unable to express sufficient amounts of the essential heat shock proteins to maintain viability.

Isolation and characterization of Escherichia coli mutants that lack the heat shock sigma factor sigma 32

The product of the Escherichia coli rpoH (htpR) gene, sigma 32, is required for heat-inducible transcription of the heat shock genes. Previous studies on the role of sigma 32 in growth at low temperature and in gene expression involved the use of nonsense and missense rpoH mutations and have led to ambiguous or conflicting results. To clarify the role of sigma 32 in cell physiology, we have constructed loss-of-function insertion and deletion mutations in rpoH. Strains lacking sigma 32 are extremely temperature sensitive and grow only at temperatures less than or equal to 20 degrees C. There is no transcription from the heat shock promoters preceding the htpG gene or the groESL and dnaKJ operons; however, several heat shock proteins are produced in the mutants. GroEL protein is present in the rpoH null mutants, but its synthesis is not inducible by a shift to high temperature. The low-level synthesis of GroEL results from transcription initiation at a minor sigma 70-controlled promoter for the groE operon. DnaK protein synthesis cannot be detected at low temperature, but can be detected after a shift to 42 degrees C. The mechanism of this heat-inducible synthesis is not known. We conclude that sigma 32 is required for cell growth at temperatures above 20 degrees C and is required for transcription from the heat shock promoters. Several heat shock proteins are synthesized in the absence of sigma 32, indicating that there are additional mechanisms controlling the synthesis of some heat shock proteins.

Mutations in the rpoH (htpR) gene of Escherichia coli K-12 phenotypically suppress a temperature-sensitive mutant defective in the sigma 70 subunit of RNA polymerase

Escherichia coli K-12 strain 285c contains a mutation in rpoD, the gene encoding the sigma subunit of RNA polymerase. The 70-kilodalton sigma polypeptide encoded by this allele is unstable, and this instability leads to temperature-sensitive growth. We describe the isolation and characterization of four temperature-resistant pseudorevertants of 285c that can grow at high temperature. Each of these revertants increased the stability of the sigma 70 mutant protein. The map position of the suppressor mutations was close to that of the rpoH (htpR) gene. A multicopy plasmid containing the intact rpoH gene restored the temperature-sensitive phenotype. Marker rescue experiments established the positions of three of the alleles within the rpoH gene. One mutation has been sequenced and causes a leucine-to-tryptophan change 7 amino acids from the carboxyl terminus of the rpoH gene product.