System-level recommendations for improved wellness for gynecologic oncologists: A Society of Gynecologic Oncology Review

Burnout and its negative sequelae are a persistent problem in gynecologic oncology, threatening the health of our physician workforce. Individual-level interventions such as stress management training, physical activity, and sleep hygiene only partially address this widespread, systemic crisis rooted in the extended work hours and stressful situations associated with gynecologic oncology practice. There is an urgent need for systematic, institution-level changes to allow gynecologic oncologists to continue the crucial work of caring for people with gynecologic cancer. We present recommendations for institution-level changes which are grounded in the framework presented by the National Plan for Health Workforce Well-Being by the National Academy of Medicine. These are aimed at facilitating gynecologic oncologists' well-being and reduction of burnout. Recommendations include efforts to create a more positive and inclusive work environment, decrease administrative barriers, promote mental health, optimize electronic medical record use, and support a diverse workforce. Implementation and regular evaluation of these interventions, with specific attention to at-risk groups, is an important next step.

Enhanced recovery after surgery (ERAS®) society guidelines for gynecologic oncology: Addressing implementation challenges - 2023 update

BACKGROUND

Despite evidence supporting its use, many Enhanced Recovery After Surgery (ERAS) recommendations remain poorly adhered to and barriers to ERAS implementation persist. In this second updated ERAS® Society guideline, a consensus for optimal perioperative care in gynecologic oncology surgery is presented, with a specific emphasis on implementation challenges.

METHODS

Based on the gaps identified by clinician stakeholder groups, nine implementation challenge topics were prioritized for review. A database search of publications using Embase and PubMed was performed (2018-2023). Studies on each topic were selected with emphasis on meta-analyses, randomized controlled trials, and large prospective cohort studies. These studies were then reviewed and graded by an international panel according to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system.

RESULTS

All recommendations on ERAS implementation challenge topics are based on best available evidence. The level of evidence for each item is presented accordingly.

CONCLUSIONS

The updated evidence base and recommendations for stakeholder derived ERAS implementation challenges in gynecologic oncology are presented by the ERAS® Society in this consensus review.

Programmed cell death in Escherichia coli: some antibiotics can trigger mazEF lethality

The discovery of toxin-antitoxin gene pairs (also called addiction modules) on extrachromosomal elements of Escherichia coli, and particularly the discovery of homologous modules on the bacterial chromosome, suggest that a potential for programmed cell death may be inherent in bacterial cultures. We have reported on the E. coli mazEF system, a regulatable addiction module located on the bacterial chromosome. MazF is a stable toxin and MazE is a labile antitoxin. Here we show that cell death mediated by the E. coli mazEF module can be triggered by several antibiotics (rifampicin, chloramphenicol, and spectinomycin) that are general inhibitors of transcription and/or translation. These antibiotics inhibit the continuous expression of the labile antitoxin MazE, and as a result, the stable toxin MazF causes cell death. Our results have implications for the possible mode(s) of action of this group of antibiotics.

The regulation of the Escherichia coli mazEF promoter involves an unusual alternating palindrome

The Escherichia coli mazEF system is a chromosomal "addiction module" that, under starvation conditions in which guanosine-3',5'-bispyrophosphate (ppGpp) is produced, is responsible for programmed cell death. This module specifies for the toxic stable protein MazF and the labile antitoxic protein MazE. Upstream from the mazEF module are two promoters, P(2) and P(3) that are strongly negatively autoregulated by MazE and MazF. We show that the expression of this module is positively regulated by the factor for inversion stimulation. What seems to be responsible for the negative autoregulation of mazEF is an unusual DNA structure, which we have called an "alternating palindrome." The middle part, "a," of this structure may complement either the downstream fragment, "b," or the upstream fragment, "c". When the MazE.MazF complex binds either of these arms of the alternating palindrome, strong negative autoregulation results. We suggest that the combined presence of the two promoters, the alternating palindrome structure and the factor for inversion stimulation-binding site, all permit the expression of the mazEF module to be sensitively regulated under various growth conditions.

Regulation of Escherichia coli RelA requires oligomerization of the C-terminal domain

The E. coli RelA protein is a ribosome-dependent (p)ppGpp synthetase that is activated in response to amino acid starvation. RelA can be dissected both functionally and physically into two domains: The N-terminal domain (NTD) (amino acids [aa] 1 to 455) contains the catalytic domain of RelA, and the C-terminal domain (CTD) (aa 455 to 744) is involved in regulating RelA activity. We used mutational analysis to localize sites important for RelA activity and control in these two domains. We inserted two separate mutations into the NTD, which resulted in mutated RelA proteins that were impaired in their ability to synthesize (p)ppGpp. When we caused the CTD in relA(+) cells to be overexpressed, (p)ppGpp accumulation during amino acid starvation was negatively affected. Mutational analysis showed that Cys-612, Asp-637, and Cys-638, found in a conserved amino acid sequence (aa 612 to 638), are essential for this negative effect of the CTD. When mutations corresponding to these residues were inserted into the full-length relA gene, the mutated RelA proteins were impaired in their regulation. In attempting to clarify the mechanism through which the CTD regulates RelA activity, we found no evidence for competition for ribosomal binding between the normal RelA and the overexpressed CTD. Results from CyaA complementation experiments of the bacterial two-hybrid system fusion plasmids (G. Karimova, J. Pidoux, A. Ullmann, and D. Ladant, Proc. Natl. Acad. Sci. USA 95:5752-5756, 1998) indicated that the CTD (aa 564 to 744) is involved in RelA-RelA interactions. Our findings support a model in which RelA activation is regulated by its oligomerization state.

Addiction modules and programmed cell death and antideath in bacterial cultures

In bacteria, programmed cell death is mediated through "addiction modules" consisting of two genes. The product of the second gene is a stable toxin, whereas the product of the first is a labile antitoxin. Here we extensively review what is known about those modules that are borne by one of a number of Escherichia coli extrachromosomal elements and are responsible for the postsegregational killing effect. We focus on a recently discovered chromosomally borne regulatable addiction module in E. coli that responds to nutritional stress and also on an antideath gene of the E. coli bacteriophage lambda. We consider the relation of these two to programmed cell death and antideath in bacterial cultures. Finally, we discuss the similarities between basic features of programmed cell death and antideath in both prokaryotes and eukaryotes and the possibility that they share a common evolutionary origin.

rexB of bacteriophage lambda is an anti-cell death gene

In Escherichia coli, programmed cell death is mediated through "addiction modules" consisting of two genes; the product of one gene is long-lived and toxic, whereas the product of the other is short-lived and antagonizes the toxic effect. Here we show that the product of lambdarexB, one of the few genes expressed in the lysogenic state of bacteriophage lambda, prevents cell death directed by each of two addiction modules, phd-doc of plasmid prophage P1 and the rel mazEF of E. coli, which is induced by the signal molecule guanosine 3',5'-bispyrophosphate (ppGpp) and thus by amino acid starvation. lambdaRexB inhibits the degradation of the antitoxic labile components Phd and MazE of these systems, which are substrates of ClpP proteases. We present a model for this anti-cell death effect of lambdaRexB through its action on the ClpP proteolytic subunit. We also propose that the lambdarex operon has an additional function to the well known phenomenon of exclusion of other phages; it can prevent the death of lysogenized cells under conditions of nutrient starvation. Thus, the rex operon may be considered as the "survival operon" of phage lambda.

Regulation of the Epstein-Barr viral immediate early BRLF1 promoter through a distal NF1 site

The immediate early BRLF1 and BZLF1 promoters of Epstein-Barr virus are crucial for triggering the replicative cycle of the virus. To better understand the cell type dependence of the lytic cycle we conducted an analysis of the BRLF1-promoter in the epithelial cell line HeLa and the lymphoid cell line IM9. To analyze promoter activities, transient transfections with 5'-deletions of the BRLF1-promoter in front of luciferase as reporter gene were conducted. Besides the already known cis-acting elements of the promoter close to the TATA-box, more distal elements were located and functionally tested. A nuclear factor 1 consensus site was found to act positively in HeLa cells, but did not in lymphoid IM9 cells. The NF1 site was shown to bind protein by electrophoretic mobility shift assays, antibody-supershifts and in vitro footprinting. Thus, a protein belonging to the nuclear factor 1 family of proteins was identified as additional cellular trans-acting factor for the BRLF1-promoter besides the already described factors Sp1, Zta and Zif268.

Analysis of the shut-off of ribosomal RNA promoters in Escherichia coli upon entering the stationary phase of growth

Most bacterial RNA consists of stable RNA which is composed of rRNA and tRNA. We have followed by primer extension analysis the level of ribosomal RNA synthesis along the growth phases of a cell culture. A sharp drop in rRNA synthesis was observed upon the transition from the exponential to the stationary phase of growth. Our results demonstrate that an effective shut-off of rRNA synthesis occurs also in the absence of ppGpp. Mutations in the host factors Fis and H-NS, which are known to regulate rrn P1 promoters, did not affect the shut-off process of ribosomal RNA promoters. We also tested the effect of RpoS, the sigma factor known to induce a number of genes in the stationary phase. It was shown that the host factors Fis, H-NS and RpoS do not play a major role in the regulation of the shut-off process of rRNA synthesis. The results presented demonstrate that the rate of rRNA synthesis provides a sensitive measure of the growth phase of the bacterial culture.

An Escherichia coli chromosomal "addiction module" regulated by guanosine [corrected] 3',5'-bispyrophosphate: a model for programmed bacterial cell death

"Addiction modules" consist of two genes. In most of them the product of one is long lived and toxic while the product of the second is short lived and antagonizes the toxic effect; so far, they have been described mainly in a number of prokaryotic extrachromosomal elements responsible for the postsegregational killing effect. Here we show that the chromosomal genes mazE and mazF, located in the Escherichia coli rel operon, have all of the properties required for an addiction module. Furthermore, the expression of mazEF is regulated by the cellular level of guanosine [corrected] 3',5'-bispyrophosphate, the product of the RelA protein under amino acid starvation. These properties suggest that the mazEF system may be responsible for programmed cell death in E. coli and thus may have a role in the physiology of starvation.

Conserved and divergent expression aspects of the Drosophila segmentation gene hunchback in the short germ band embryo of the flour beetle Tribolium

The segmentation gene hunchback (hb) plays a central role in determining the anterior-posterior pattern in the Drosophila embryo. We have cloned the homologue of hb from the flour beetle Tribolium and show that, on the basis of its expression pattern, most of its functions seem to be conserved between these two species. Like Drosophila, Tribolium has a maternal hb expression that appears to be under translational control by a factor at the posterior pole of the embryo. The maternal expression is followed by a zygotic expression in the region of the developing head and thoracic segments. During germ band extension, a posterior expression domain appears that is likely to be homologous to the posterior blastoderm expression of hb in Drosophila. These observations suggest that hb may have the same functions in early Drosophila and Tribolium development, despite the different types of embryogenesis in these two species (long versus short germ development). One differing aspect of hb expression in Tribolium concerns a structure that is not present in Drosophila, namely the serosa. An hb expression domain at the anterior pole precisely demarcates the border between the extraembryonic serosa and the embryonic field in the Tribolium embryo at an early stage, and hb protein remains expressed in the serosa cells until the end of embryogenesis.

Nucleoprotein complexes and DNA 5'-ends at oriP of Epstein-Barr virus

Understanding protein-DNA interactions in vivo at origins of DNA replication throughout the cell cycle may shed further insight on the mechanisms of initiation and replication control. The Burkitt's lymphoma cell line Raji harbors multiple copies of latent Epstein-Barr virus. Once per cell cycle the origin of plasmid replication of Epstein-Barr virus provides replication function in cis for the viral DNA. Here we examined in vivo nucleoprotein complexes on the initiator element of the origin before and after DNA synthesis. For this purpose Raji cells were synchronously growth arrested in G1 phase by mimosine and in mitosis by colchicine, respectively. The association of the initiator element with proteins was visualized by footprinting with dimethyl sulfate and ligation mediated polymerase chain reaction. Methylation patterns indicated a novel binding activity within each element of a nonamer repeated three times at the initiator element. This activity was strongly diminished in mitotic cells. Furthermore, 5'-ends of Epstein-Barr virus DNA were mapped to the nonamers by ligation mediated polymerase chain reaction, suggesting potential initiation sites for replication from DS.

ppGpp-mediated regulation of DNA replication and cell division in Escherichia coli

ppGpp serves as an alarmon in prokaryotes, distributing and coordinating different cellular processes according to the nutritional potential of the growth medium. This work is interpreted as favoring the view that, in addition to its previously documented role in regulating the rate of ribosome synthesis, ppGpp participates in coordinating DNA replication and cell division. We studied the effects of ppGpp on the cell division cycle, using cells containing plasmid pSM11 that codes for the 55-kDa truncated RelA protein under the inducible Ptac promoter. In this system it was found that the rate of initiation of new rounds of DNA replication is inversely correlated with the intracellular level of ppGpp. Furthermore, ppGpp levels similar to those found during the activation of stringent control inhibited replication initiation, in a manner comparable to that resulting from inhibition of protein synthesis by amino acid starvation or by chloramphenicol addition. However, in contrast to chloramphenicol treatment, elevated ppGpp levels did not block septum formation, and, in fact, there is some evidence for enhanced septation. As a result, the residual cell division following elevation in ppGpp levels was higher than after chloramphenicol treatment, resulting in cells with a size similar to that of stationary phase cells.

Expression of the genes coding for the Escherichia coli integration host factor are controlled by growth phase, rpoS, ppGpp and by autoregulation

Transcriptional control of the himA and the himD/hip genes coding for the two subunits of the integration host factor (IHF) was investigated. The promoters for the two genes were identified by the use of primer extension and S1 analysis. Expression from both promoters was found to increase as the cells enter stationary phase. Mutation in rpoS, known to be induced upon entry to stationary phase, dramatically reduced the growth-phase response of the himA P4 promoter but had only a small effect on the induction of the himD/hip promoter. The increased activity of both promoters required the presence of the relA and spoT genes, suggesting that ppGpp plays a major role in the response to stationary phase. An artificial increase in ppGpp in exponentially growing cells induced a rapid increase in himA P4 and himD/hip mRNA levels. Experiments with a mutant defective in rpoS showed that the response of the himA P4 promoter to high ppGpp levels was greatly reduced while that of himD/hip was only slightly affected. Therefore, it seems that different mechanisms involving RpoS and ppGpp regulate the growth-phase response of the two promoters. We propose that the effect of ppGpp on himA P4 is mediated via RpoS whereas the himD/hip promoter is affected by ppGpp independently of RpoS. Expression of the himD/hip and himA genes was found to be subject to negative autoregulation. IHF-binding sites, implicated in autoregulation, were found to overlap both the himD/hip and himA P4 promoters. An additional IHF-binding site was found upstream of the himD/hip promoter. All three sites show low binding affinity to IHF suggesting that autoregulation can take place only after sufficiently high levels of IHF accumulate in the cell.

Isolated P2 rRNA promoters of Escherichia coli are strong promoters that are subject to stringent control

Ribosomal RNA synthesis in Escherichia coli is under stringent control. The seven rRNA operons are highly conserved and are each transcribed from two tandem promoters, P1 and P2, which are located about 120 base-pairs apart. In exponentially growing cells the majority of the transcripts are initiated at the P1 promoters. The P1 promoters are highly regulated, and are under stringent as well as growth rate controls. Here we demonstrate that transcription from the rrnA P1 promoter diminishes P2 expression. In the absence of P1, the P2 promoter acts as a rather strong promoter. Insertion of a transcription terminator between P1 and P2 eliminates the inhibition of P2 by P1, suggesting that the physical movement of RNA polymerase originating at P1 and progressing along the P2 promoter is necessary for the interference process to take place. Similarly to P1, the solitary P2 promoter is subject to stringent control.

Differential regulation of target genes by different alleles of the segmentation gene hunchback in Drosophila

hunchback (hb) is a key regulatory gene in the early segmentation gene hierarchy of Drosophila. It codes for a transcription factor of the Cys2-His2 zinc finger type and shows two separate zinc finger domains in its coding region. hb forms a morphogenetic gradient in the middle of the embryo that is required for setting the spatial boundaries of several target genes. We have analyzed the molecular lesions found in the different hb alleles and have studied the differential effects of these alleles on a number of such target genes. We find that in mutants in which the HB protein lacks a functional second finger domain, the regulation of the target genes Krüppel (Kr) and knirps (kni) is differentially affected. While this domain is required for the correct regulation of Kr, it is not necessary for the repression of kni. Furthermore, mutations affecting this domain lead to a decreased protein stability. The integration of the expression pattern of target genes was found to be distorted in a second class of mutants between the two finger domains which lead to gain of function or neomorphic phenotypes. The effects of these mutations were studied in detail and it was found that they fall into two classes, the first one interfering with the function of the maternal hb product, the second leading to a delayed segmentation. The function of the latter class appears to be linked to the secondary expression of hb in the parasegment 4 (PS4) stripe at blastoderm stage.

A relA(S) suppressor mutant allele of Bacillus subtilis which maps to relA and responds only to carbon limitation

The histidine analog 3-amino-1,2,4-triazole (AT) was used for the selection of spontaneous AT-resistant revertants of a relA mutant of Bacillus subtilis. One of these revertants, L3, showed a unique phenotype; it did not respond to amino acid starvation, like the relA mutant, but it did respond to glucose starvation by the accumulation of (p)ppGpp, unlike its parent. Genetic analysis revealed that this suppressor mutant (relA(S)) allele mapped to the relA locus at 239 degrees on the B. subtilis chromosome.

Regulatory and coding regions of the segmentation gene hunchback are functionally conserved between Drosophila virilis and Drosophila melanogaster

The segmentation gene hunchback (hb) is involved in setting up the anterior-posterior axis of the Drosophila embryo. It is expressed maternally and zygotically and it plays a key role in integrating the effects of the anterior and posterior maternal systems. The hb gene from D. virilis has previously been cloned and was shown to be well conserved in its coding region, but less so in its upstream region which shows a more patchy pattern of conserved and diverged sequences. This work deals with the functional conservation of hb between the two species. We have mapped two additional regulatory elements for the expression of hb in the early embryo, namely the enhancer for the maternal expression and the enhancer region for the late blastoderm expression. Fragments containing these two elements, the previously identified bicoid dependent element for the early blastoderm expression of hb and the coding region were taken from D. virilis and tested in the D. melanogaster background. We find that all enhancer elements as well as the coding region are functionally conserved between the two species. Comparison of the upstream sequences that include the enhancer region for the late blastoderm expression reveal seven highly conserved blocks. Some of these contain consensus binding sites for transregulatory factors that are likely to control the respective expression domains.

The lytic transition of Epstein-Barr virus is imitated by recombinant B-cells

Lytic transition of Epstein-Barr virus (EBV) is initiated by distinct immediate early regulators of the viral cycle, in synchronization to temporary, permissive conditions during host cell differentiation. We developed eukaryotic vectors suitable to imitate the processes involved in lytic transition in cell culture systems. Two stable B cell lines were established: R59Z activator cells were used to induce lytic EBV expression in a constitutive manner by the production of the BZLF 1 trans-activator (Zta). R7-57 reporter cells, on the other hand, signaled induced activity of the lytic origin of EBV replication (ori Lyt). Different modes, like chemical induction, lytic superinfection with EBV and single gene trans-activation converted the recombinant ori Lyt element in R7-57 reporter cells. BZLF 1, transiently expressed in R7-57 reporter cells, was the only EBV trans-activator found, sufficient in inducing the viral lytic cycle. Basing on these experiments, trans-cellular activation of EBV was tested by cocultivation of BZLF 1-expressing R59Z activator cells with the R7-57 reporter line. No lytic effect on the reporter cells could be measured, neither by cocultivation of activator cells nor by coincubation of BZLF 1-containing cell lysates. Latency breaking activity, however, was transferred from activator to reporter cells when active, exogenous virus was added. The cell system described in these experiments provides a tool for the detection of EBV reactivation and demonstrates the potential of the lytic regulatory gene BZLF 1.

Function of a relaxed-like state following temperature downshifts in Escherichia coli

Temperature downshifts of Escherichia coli throughout its growth range resulted in transient growth inhibition and a cold shock response consisting of transient induction of several proteins, repression of heat shock proteins, and, despite the growth lag, continued synthesis of proteins involved in transcription and translation. The paradoxical synthesis of the latter proteins, which are normally repressed when growth is arrested, was explored further. First, by means of a nutritional downshift, a natural stringent response was induced in wild-type cells immediately prior to a shift from 37 to 10 degrees C. These cells displayed decreased synthesis of transcriptional and translational proteins and decreased induction of cold shock proteins; also, adaptation for growth at 10 degrees C was delayed, even after restoration of the nutrient supplementation. Next, the contribution of guanosine 5'-triphosphate-3'-diphosphate and guanosine 5'-diphosphate-3'-diphosphate, collectively abbreviated (p)ppGpp, to the alteration in cold shock response was studied with the aid of a mutant strain in which overproduction of these nucleotides can be artificially induced. Induction of (p)ppGpp synthesis immediately prior to shifting this strain from 37 to 10 degrees C produced results differing only in a few details from those described above for nutritional downshift of the wild-type strain. Finally, shifting a relA spoT mutant, which cannot synthesize (p)ppGpp, from 24 to 10 degrees C resulted in a greater induction of the cold shock proteins, increased synthesis of transcriptional and translational proteins, decreased synthesis of a major heat shock protein, and faster adaptation to growth than for the wild-type strain. Our results indicate that the previously reported decrease in the (p)ppGpp level following temperature downshift plays a physiological role in the regulation of gene expression and adaptation for growth at low temperature.

NhaR, a protein homologous to a family of bacterial regulatory proteins (LysR), regulates nhaA, the sodium proton antiporter gene in Escherichia coli

On the basis of protein homology, nhaR has previously been shown to belong to a large family of regulatory proteins, the LysR family (Henikoff, S., Haughn, G.W., Calvo, J.M., and Wallace, J.C. (1988) Proc. Natl. Acad. Sci. U. S. A. 85, 6602-6606). In this work we show that nhaR is a regulator of nhaA, a gene encoding a Na+/H+ antiporter in Escherichia coli. Multicopy plasmid bearing nhaR enhances the Na(+)-dependent induction of a chromosomal nhaA'-'lacZ fusion. Extracts derived from cells overexpressing nhaR exhibit specific DNA binding capacity to the upstream sequences of nhaA. Construction of an nhaR deletion mutant (OR100) shows that nhaR is required in addition to nhaA to tolerate the extreme conditions under which nhaA is indispensable. Whereas OR100 grows like the wild type at neutral pH even at high Na+ concentrations (700 mM), it becomes much more sensitive to Na+ (greater than 300 mM) at pH 8.5; furthermore, OR100 is more sensitive to Li+ (100 mM) than the wild type. Nevertheless, the phenotype of OR100, which is more resistant to Na+, Li+, and alkaline pH than a delta nhaA strain (NM81), implies that the regulation exerted by nhaR is not complete and that some expression of nhaA exists in OR100. Accordingly, the effect of nhaR in cells is dependent on the level of nhaA. OR200, a nhaA and nhaR deletion mutant, has the same phenotype as NM81. Multicopy plasmid bearing nhaR does not change the phenotype of either OR200 or NM81. On the other hand, multicopy nhaA renders the cells Li(+)- and and Na(+)-resistant even without nhaR.

Expression of a sodium proton antiporter (NhaA) in Escherichia coli is induced by Na+ and Li+ ions

Regulation of expression of nhaA, the gene which encodes a Na+/H+ antiporter in Escherichia coli has been studied. Two promoters have been identified in the upstream sequence of the gene and the corresponding start point of transcription mapped by primer extension. Monitoring the beta-galactosidase activity of a chromosomal translation fusion of nhaA'-'lacZ show that at pH 7.5 the gene is induced, within 1 h, by 100 mM of either Li+ or Na+. Change of pH between 6.5 and 8.5 by itself does not increase expression of the gene but it markedly increases the sensitivity of the expression system to the ions. At pH 7.5 maximal induction is obtained by 100 mM NaCl, whereas at pH 8.6, 10 mM NaCl elicit similar response. The pattern of regulation of nhaA reflects its importance in adaptation to high salinity and alkaline pH in E. coli.

Residual guanosine 3',5'-bispyrophosphate synthetic activity of relA null mutants can be eliminated by spoT null mutations

It was known previously that 1) the relA gene of Escherichia coli encodes an enzyme capable of guanosine 3',5'-bispyrophosphate (ppGpp) synthesis, 2) an uncharacterized source of ppGpp synthesis exists in relA null strains, and 3) cellular degradation of ppGpp is mainly due to a manganese-dependent ppGpp 3'-pyrophosphohydrolase encoded by the spoT gene. Here, the effects of spoT gene insertions and deletions are compared with analogous alterations in neighboring genes in the spo operon and found to be lethal in relA+ strains as well as slower growing in relAl backgrounds than delta relA hosts. Cells with null alleles in both the relA and spoT genes are found no longer to accumulate ppGpp after glucose exhaustion or after chelation of manganese ions by picolinic acid addition; the inability to form ppGpp is reversed by a minimal spoT gene on a multicopy plasmid. Strains apparently lacking ppGpp show a complex phenotype including auxotrophy for several amino acids and morphological alterations. We propose that the SpoT protein can either catalyze or control the alternative pathway of ppGpp synthesis in addition to its known role as a (p)ppGpp 3'-pyrophosphohydrolase. We favor the possibility that the SpoT protein is a bifunctional enzyme capable of catalyzing either ppGpp synthesis or degradation.

Overexpression of the relA gene in Escherichia coli

Intracellular levels of guanosine 3',5'-bispyrophosphate (ppGpp) governed by the relA gene are normally regulated by aminoacyl-tRNA availability for protein synthesis. An experimental system is described in which cellular levels of ppGpp are controlled instead by induction of plasmid pKK223-3 derivatives with the relA structural gene, or portions thereof, under control of the Ptac promoter. In amino acid-rich media, isopropyl-1-thio-beta-D-galactopyranoside induction of transcription of the wild type relA gene in pSM10 yields about a 100-fold overexpression of a metabolically stable, full length (743 amino acid) RelA protein to levels approximating the number of cellular ribosomes. This overexpression is accompanied by a roughly parallel and relC-dependent elevation of ppGpp levels. Induction of a relA gene deletion mutant in pSM11 containing 455 amino-terminal amino acids results in much lower levels of expression of a metabolically unstable 55-kDa protein and elevated ppGpp levels that are almost equivalent to induced pSM10 and are relC-independent. Induction of a larger deletion in pSM12 containing 331 amino-terminal amino acids does not provoke ppGpp accumulation. We are able to elicit high levels of ppGpp without changing nutritional abundance and without massive overexpression of the RelA protein by inducing the metabolically unstable, truncated RelA protein. We find the effects of elevated ppGpp levels to include a slowing of growth, an inhibition of stable RNA accumulation, an inhibition of cellular rrn P1 promoter activities as measured by primer extension, and changes in the pattern of gene expression viewed by two-dimensional electrophoresis of cellular proteins.

Characterization of the relA1 mutation and a comparison of relA1 with new relA null alleles in Escherichia coli

The most widely studied "relaxed" mutant of the relA locus, the relA1 allele, is shown here to consist of an IS2 insertion between the 85th and 86th codons of the otherwise wild-type relA structural gene, which normally encodes a 743-amino acid (84 kDa) protein. The RelA protein is a ribosome-dependent ATP:GTP (GDP) pyrophosphoryltransferase that is activated during the stringent response to amino acid starvation and thereby occasions the accumulation of guanosine 3',5'-bispyrophosphate (ppGpp). We propose that the IS2 insertion functionally splits the RelA protein into two (alpha and beta) peptide fragments which can complement each other in trans to yield residual ppGpp synthetic activity; neither fragment shows this activity when expressed alone. Cell strains with a single copy relA null allele show physiological behavior that is much the same as relA1 mutant strains. Both relA1 and relA null strains accumulate ppGpp during glucose starvation and do not accumulate ppGpp during the stringent response. The presence of ppGpp in verifiable relA null strains is interpreted as unequivocal evidence for an alternate route of ppGpp synthesis that exists in addition to the relA-dependent reaction.

Ribosome associated protein(s) specifically bind(s) to the upstream activator sequence of the E. coli rrnA P1 promoter

A sequence located upstream to the E. coli rrnA P1 promoter is required for optimal promoter activity. Deletion of this sequence reduces in vivo transcription by 90%. Substitution of this upstream activating sequence with the unrelated bent DNA sequence of the kinetoplast of Crithidia fasciculata, restores in vivo expression to high levels. Cellular proteins which are present only in exponentially growing cells bind specifically to intact rrnA P1, but do not bind to the promoter missing the upstream activating sequence. These proteins are associated with the 30S ribosomal subunits but can be washed off with concentrated salt. The correlation between the binding activity and cell growth rate suggests a role for these proteins in the transcriptional control of rRNA synthesis.

Protein sequences encoded by the relA and the spoT genes of Escherichia coli are interrelated

relA and spoT are designations for two unlinked Escherichia coli genes whose products function in the synthesis and degradation of guanosine 3',5'-bispyrophosphate during the stringent regulatory response to amino acid deprivation. The RelA protein catalyzes an ATP:GTP 3'-pyrophosphoryl group transfer reaction, and the SpoT protein has a guanosine 3',5'-bispyrophosphate 3'-pyrophosphohydrolyase activity. Both genes have been sequenced recently; the relA gene produces an 84-kDa protein, and the spoT gene is deduced to encode a 79-kDa protein. We report here that the protein sequences of the relA and spoT genes are extensively interrelated.

Recombination and replication of plasmid-like derivatives of a short section of the mitochondrial chromosome of Neurospora crassa

The 21-kbp mitochondrial chromosome of the stp-ruv strain of Neurospora crassa undergoes regional amplification yielding plasmid-like supercoiled circles varying in size from subunit length to very high multimers. A comparison of the base sequence of the five plasmids studied, with the region of the chromosome from which they were derived, indicated that the amplified chromosomal segments were determined by a recombination-excision process near or within two structurally distinctive regions. One of these, consisting of nearly uninterrupted strings of Cs and Gs straddling tandem PstI site direct repeats, could form an extended hairpin loop with only a few mismatches. It was found at or near the 5' exchange point of all of the plasmids. An extended 35-bp sequence containing 17-bp direct repeats was the primary 3' site of exchange. Base sequence changes were found in the vicinity of exchange points. Most notable of these was a G insertion and T to C transition within a section of the 5' region likely to form a hairpin loop, suggesting the involvement of a mismatch repair-like mechanism in the recombination process. The sequence, TATATAGACATATA, was identified as a likely candidate for the site of replication initiation. A nearly identical sequence was found common to all of the corresponding plasmids of Podospora anserina and was reported near the presumed replication origin of the Drosophila yakuba mitochondrial chromosome. A search of GenBank revealed a remarkable association of the consensus sequence, TATATAGAXATATA, with the plus strand of organelle DNA.

The nucleotide sequence and characterization of the relA gene of Escherichia coli

The relA gene product of Escherichia coli is known to be responsible for the synthesis of guanosine 3',5'-bispyrophosphate (ppGpp) during the stringent response to amino acid starvation. This report presents the sequence of the relA gene region and assignment of its 743-codon open reading frame by the following criteria: 1) genetic complementation of ppGpp synthesis in a relaxed (relA1) mutant during the stringent response; 2) changes in 3-aminotriazole resistance during growth to mimic a relA+ phenotype; 3) verification of the presence of an amber codon at the normal carboxyl terminus of the relA gene; and 4) immunological assays of expression of the RelA protein. The apparent molecular mass of the cloned relA gene product is calculated to be 83,856 daltons and as visualized by immunoblotting is identical to that of the previously characterized protein. A promoter has been identified that directs relA gene transcription towards the pyrG gene, in a counterclockwise direction on the E. coli chromosome. Genomic Southern blot analyses verify that the relA regions cloned and subjected to nucleotide sequence analysis correspond to homologous regions on the E. coli chromosome.

Promoter of the Mycoplasma pneumoniae rRNA operon

RNA transcripts starting from the 5' end of the single Mycoplasma pneumoniae rRNA operon were analyzed by several methods. By primer extension analysis a start site was found 62 nucleotides upstream from the start site of the 16S rRNA. This site was preceded by a putative Pribnow box; however, a defined -35 recognition region was absent. The cloned rRNA operon was transcribed in vitro by using purified RNA polymerase of Escherichia coli. A single start site could be demonstrated within a few nucleotides of the start site found by primer extension analysis of M. pneumoniae transcripts. When fragments from the cloned operon were used as hybridization probes, S1 nuclease mapping yielded a single transcript extending approximately 193 nucleotides upstream from the 16S rRNA start site. The region surrounding this endpoint did not resemble any known promoter sequence. Dot blot hybridization of M. pneumoniae RNA to three oligonucleotides consisting of nucleotides -5 to -21, -38 to -54, and -112 to -132 (from the start of the 16S rRNA gene) indicated that most rRNA transcripts were processed at the stem site preceding the 16S rRNA gene. The majority of the longer precursor transcripts, extending beyond this point, did not extend further upstream to an oligonucleotide consisting of nucleotides -112 to -132. It was concluded that transcription of the rRNA operon of M. pneumoniae is initiated by a single promoter. The nucleotide sequence of the region is presented.

Promoters of Mycoplasma capricolum ribosomal RNA operons: identical activities but different regulation in homologous and heterologous cells

The 5' region of the rRNA operon, rrnA, of M. capricolum was cloned. Sequence analysis revealed two tRNA genes, tRNA(leu) and tRNA(lys), upstream to the promoter of the rRNA operon. The in vivo transcription start sites of the rRNA operon and of the tRNA genes were mapped. The same promoters used by M. capricolum RNA polymerase are also recognized by E. coli RNA polymerase both in vivo and in vitro. We find that high levels of ppGpp in E. coli, resulting from amino acid starvation or from spoT mutation, activate rather than repress the transcription of the mycoplasma rrnA operon.

A patient of German descent with (delta beta)0-thalassemia carrying the Sicilian type deletion of the delta and beta globin genes

A deletion-type (delta beta)0-thalassemia with elevated production of fetal hemoglobin (Hb F) is described. The patient, homozygous for the disease, presented a clinical picture of beta-thalassemia intermedia. DNA analysis demonstrated that the deletion removed about 13 kb from the beta-globin cluster, including part of delta and the complete beta gene. The deletion appears to be identical to the previously described Sicilian deletion. Its presence in the homozygous state in a patient from Central Europe suggests that the deleted chromosome may be rather prevalent in that area.

Spiroplasma plasmids

Extrachromosomal DNA, constituting plasmids or replicative forms of viruses, has been detected in a variety of spiroplasmas, particularly in Spiroplasma citri. Only a few of the S. citri plasmids were characterized by restriction enzyme mapping, and essentially nothing is known on functions encoded by the plasmids. Our studies revealed in S. citri (R8A2) an 8.0-kbp plasmid that differed from previously described plasmids in its restriction map. It was also clonable in pBR322. The plasmid, named pRA1, was found in large quantities as free plasmid in S. citri (R8A2) subclones of low passage level. In subclones of higher passage levels, free plasmid was replaced by plasmid sequences integrated into the spiroplasma chromosome, as revealed by Southern hybridization blots of digested spiroplasmal DNA with nick-translated pRA1 or its recombinant as probes. Significant quantities of integrated plasmid sequences were also observed in S. kunkelii and in Spiroplasma sp. P40. Small quantities of free and/or integrated plasmid DNA were detected in some spiroplasmas serologically and genotypically remote from S. citri. Chromosome-integrated pRA1 sequences were cloned into the Escherichia coli plasmids pUC13 and M13. Hybridization tests and restriction maps of these clones indicated that the integrated plasmid sequences consisted of small repetitive sequences inserted into specific sites on the spiroplasma chromosome. Despite the large number of the inserts they do not appear to affect significantly gene expression in the spiroplasma. Due to the abundance of free and integrated pRA1 in S. citri, nick-translated pRA1 was effective as a DNA probe in detecting small numbers of S. citri in infected periwinkle plants and leafhoppers.

Transcription control elements of the Mycoplasma pneumoniae rRNA operon

The single RNA operon of Mycoplasma pneumoniae was cloned into a lambda vector and subcloned into pBR322. This was carried out in order to enable the analysis of the transcription control regions of this operon. S1 nuclease mapping was used to locate the 5' ends of RNA transcripts synthesized from the operon. The 5' ends of the 23S, 16S, and a precursor RNA synthesized in vivo in M. pneumoniae were mapped on the DNA template. Preliminary in vitro transcription experiments using RNA polymerase of Escherichia coli led to the conclusion that E. coli recognizes one promoter in the 5' region of the M. pneumoniae rRNA operon. The startsite of the in vitro transcript seems to lie downstream from the 5' end of the M. pneumoniae precursor transcript. Preliminary sequencing of the 5' regions of the M. pneumoniae rRNA operon and of the M. capricolum rRNA B operon enabled their comparison to each other and to known sequences from other organisms.

Kindling induces a long-lasting change in the activity of a hippocampal membrane calmodulin-dependent protein kinase system

Septal kindling has been shown to produce a long-lasting decrease in endogenous calcium/calmodulin-dependent phosphorylation of hippocampal synaptic plasma membrane proteins, including two major bands of approximately 50,000 and 60,000 Daltons. These two proteins differ from the B-50 protein and tubulin, as evidenced by differences in migration in SDS-PAGE gels and by lack of cross-immunoreactivity with specific antibodies. Identity of these two proteins with the rho and sigma subunits of purified calmodulin-dependent kinase (CaM Kinase II) is suggested by similar migration in SDS-PAGE and two-dimensional gels, by similar calmodulin binding in two-dimensional gels, and similar 125I-peptide mapping of the 50,000 Dalton protein. These results demonstrate that septal kindling is associated with changes in the activity of a major Ca2+/calmodulin-dependent kinase system in hippocampal synaptic plasma membrane. This long-lasting modulation of kinase activity may provide a molecular insight into some aspects of neuronal plasticity.

Beta-thalassemia: analysis of mRNA precursors of a mutant human globin gene with defective splicing using peripheral blood nucleated red blood cells

Studies on the effects of thalassemic mutations on gene function in vivo have clinical as well as scientific implications. Usually these studies have been performed on nucleated red blood cell (RBC) precursors normally present in bone marrow. Many patients with beta-thalassemia are splenectomized and may have high levels of nucleated RBC, orthochromatic normoblasts, in their peripheral blood (1-5% of total RBC). The possibility of exploiting these cells instead of bone marrow as a source for nuclear and cytoplasmic RNA for expression studies was investigated. A simple procedure was developed for enrichment for normoblasts in blood samples withdrawn from patients prior to transfusion. Globin transcripts were analyzed in RNA purified from 12 patients. Unspliced precursor beta-mRNA molecules were observed in a patient with beta o-thalassemia, homozygous for a mutation at the 5' IVS2 splice site of the beta-globin gene. Detailed analyses showed that his mature beta-mRNA was larger than normal, and that a cryptic 5' splice site, approximately 50 nucleotides downstream from the normal one, was utilized. We conclude that peripheral blood can be used as a reliable source of RNA for the analysis of the effects of beta-thalassemia mutations on gene expression and the relationship to the clinical condition. Moreover, this procedure facilitates the comparison of in vivo gene expression with the results obtained from DNA transfection experiments with cloned beta-thalassemia genes.

Procaryotic and eucaryotic traits of DNA methylation in spiroplasmas (mycoplasmas)

Differences in the type of base methylated (cytosine or adenine) and in the extent of methylation were detected by high-pressure liquid chromatography in the DNAs of five spiroplasmas. Nearest neighbor analysis and digestion by restriction enzyme isoschizomers also revealed differences in methylation sequence specificity. Whereas in Spiroplasma floricola and Spiroplasma sp. strain PPS-1 5-methylcytosine was found on the 5' side of each of the four major bases, the cytosine in Spiroplasma apis DNA was methylated only when its 3' neighboring base was adenine or thymine. In Spiroplasma sp. strain MQ-1 over 95% of the methylated cytosine was in C-G sequences. Essentially all of the C-G sequences in the MQ-1 DNA were methylated. Partially purified extracts of S. apis and Spiroplasma sp. strain MQ-1 were used to study substrate and sequence specificity of the methylase activity. Methylation by the MQ-1 enzyme was exclusively at C-G sequences, resembling in this respect eucaryotic DNA methylases. However, the MQ-1 methylase differed from eucaryotic methylases by showing high activity on nonmethylated DNA duplexes, low activity with hemimethylated DNA duplexes, and no activity on single-stranded DNA.