Using focus groups to explore caregiver transitions and needs after placement of family members living with dementia in 24-hour care homes

Objectives: Family caregivers (defined broadly as family and friends) of persons with dementia are challenged to cope with myriad stressors and changes that occur along the dementia trajectory. The purpose of this study was to explore the transitions experienced by caregivers of persons with dementia after their relative relocated to a 24-hour care home.Method: Qualitative thematic and conversational analysis were used: themes were co-created and modes of speech and syntactical patterns analysed to expose discourses related to caregiving after placement in 24-hour care homes.Results: Four main themes were co-constructed from the data analysis: living with loss, relinquishing, redefining the caregiving role, and rediscovering and recreating a new self.Discussion: Caregiving continues after placement of family members with dementia in 24-hour care homes. Caregivers are at-risk group and require ongoing support throughout the caregiving journey. Study participants reported that navigation skills such as relationship building, communication, and advocacy were particularly salient to the post-placement period, when navigating the complex health care environment was a significant obstacle. Ultimately, findings from these focus groups will be used to inform an online intervention to support caregivers of a family member with dementia residing in a 24-hour care home.

Analysis of protein kinase C theta inhibitors for the control of HIV-1 replication in human CD4+ T cells reveals an effect on retrotranscription in addition to viral transcription

HIV-1 infection cannot be cured due to reservoirs formed early after infection. Decreasing the massive CD4+ T cell activation that occurs at the beginning of the disease would delay reservoir seeding, providing a better prognosis for patients. CD4+ T cell activation is mediated by protein kinase C (PKC) theta (θ), which is involved in T-cell proliferation, as well as NF-κB, NF-AT, and AP-1 activation. We found that PKCθ activity increased viral replication, but also that HIV-1 induced higher activation of PKCθ in infected CD4+ T cells, creating a feedback loop. Therefore, specific inhibition of PKCθ activity could contribute to control HIV-1 replication. We tested the efficacy of seven PKCθ specific inhibitors to control HIV-1 replication in CD4+ T cells and selected two of the more potent and safer: CGX1079 and CGX0471. They reduced PKCθ phosphorylation at T538 and its translocation to the plasma membrane, which correlated with decreased HIV-1 retrotranscription through partial inhibition of SAMHD1 antiviral activity, rendering lower proviral integration. CGX1079 and CGX0471 also interfered with viral transcription, which would reduce the production of new virions, as well as the subsequent spread and infection of new targets that would increase the reservoir size. CGX1079 and CGX0471 did not completely abrogate T-cell functions such as proliferation and CD8-mediated release of IFN-γ in PBMCs from HIV-infected patients, thereby avoiding general immunosuppresion. Consequently, using PKCθ inhibitors as adjuvant of antiretroviral therapy in recently infected patients would decrease the pool of activated CD4+ T cells, thwarting proviral integration and reducing the reservoir size.

CGX1037 is a novel PKC isoform delta selective inhibitor in platelets

Platelets upon activation change their shape, aggregate and secrete alpha and dense granule contents among which ADP acts as a feedback activator. Different Protein Kinase C (PKC) isoforms have specific non-redundant roles in mediating platelet responses including secretion and thrombus formation. Murine platelets lacking specific PKC isoforms have been used to evaluate the isoform specific functions. Novel PKC isoform δ has been shown to play an important role in some pathological processes. Lack of specific inhibitors for PKCδ has restricted analysis of its role in various cells. The current study was carried out to evaluate a novel small molecule PKCδ inhibitor, CGX1037 in platelets. Platelet aggregation, dense granule secretion and western blotting experiments were performed to evaluate CGX1037. In human platelets, CGX1037 inhibited PAR4-mediated phosphorylation on PKD2, a PKCδ-specific substrate. Pre-treatment of human or murine platelets with CGX1037 inhibited PAR4-mediated dense granule secretion whereas it potentiated GPVI-mediated dense granule secretion similar to the responses observed in murine platelets lacking PKCδ· Furthermore, pre-treatment of platelets from PKCδ(-/-) mice with CGX1037 had no significant additive effect on platelet responses suggesting the specificity of CGX1037. Hence, we show that CGX1037 is a selective small molecule inhibitor of PKCδ in platelets.

The economic impact of the utilization of liver allografts with high donor risk index

The disparity between the organ supply and the demand for liver transplantation (LT) has resulted in the growing utilization of 'marginal donor' organs. While economic outcomes for subsets of 'marginal' organs have been described for renal transplantation, similar analyses have not been performed for LT. Using UNOS data for 17 710 LTs performed between 2002 and 2005, we assessed the relationship between recipient model for end-stage liver disease (MELD) score, organ quality as defined by donor risk index (DRI, Feng et al. 2005) and hospital length of stay (LOS). Single-center cost-accounting data for 338 liver transplants were then analyzed with a multivariate linear regression model to determine the estimated cost associated with a day of LOS. Overall, 8.4% of donor organs were classified as high risk (DRI > 2-2.5) and 1.9% as very high risk (DRI > 2.5). In the lowest MELD group (0-10), the LOS difference between 'ideal' donors (DRI < 1.0) and very high risk (DRI > 2.5) was 10.6 days which was associated with an estimated incremental cost of $47 986. For patients with MELD >35, the average LOS increased from 23.2 to 41.8 days when very high DRI donors were used, resulting in an estimated increase in cost of nearly $84 000. We conclude that the use of marginal liver grafts results in increased hospital costs independent of recipient risk factors.

Life-cycle and growth-phase-dependent regulation of the ubiquitin genes of Trypanosoma cruzi

BACKGROUND

Trypanosoma cruzi, the causative agent of Chagas disease, exhibits a complex life cycle that is accompanied by the stage-specific gene expression. At the molecular level, very little is known about gene regulation in trypanosomes. Complex gene organizations coupled with polycistronic transcription units make the analysis of regulated gene expression difficult in trypanosomes. The ubiquitin genes of T. cruzi are a good example of this complexity. They are organized as a single cluster containing five ubiquitin fusion (FUS) and five polyubiquitin (PUB) genes that are polycistronically transcribed but expressed differently in response to developmental and environmental changes.

METHODS

Gene replacements were used to study FUS and PUB gene expression at different stages of growth and at different points in the life cycle of T. cruzi.

RESULTS

Based on the levels of reporter gene expression, it was determined that FUS1 expression was downregulated as the parasites approached stationary phase, whereas PUB12.5 polyubiquitin gene expression increased. Conversely, FUS1 expression increases when epimastigotes and amastigotes differentiate into trypomastigotes, whereas the expression of PUB12.5 decreases when epimastigotes differentiate into amastigotes and trypomastigotes.

CONCLUSIONS

Although the level of CAT activity in logarithmic growing epimastigotes is six- to seven-fold higher when the gene was expressed from the FUS1 locus than when expressed from the PUB12.5 locus, the rate of transcription from the two loci was the same implying that post-transcriptional mechanisms play a dominant role in the regulation of gene expression.

Relationship of bone morphogenetic protein expression during osteoblast differentiation to wild type p53

We have previously shown p53 to have a specific role in osteoblast differentiation by its ability to regulate expression of certain bone specific proteins. In this study, we show mineralized matrix formation in vivo to be directly related to the presence of wild type p53 in osteoblastic osteosarcoma cells. In order to further understand the importance of p53 in differentiation, we investigated the relationship between p53 and Bone Morphogenetic Proteins (BMPs) (BMP 1, 2, 3A, 3B (GDF-10), 4, 5, 6, 7, 8A and 8B) during osteoblast differentiation. The expression of several BMPs were tested using RNase Protection Assay in differentiating ROS17/2.8 osteoblastic osteosarcoma cells. The expression of BMPs 1, 2, 3a, 3b and 7 showed time dependent modulation during in vitro differentiation. In order to determine if p53 has a role in this process, we used a murine osteosarcoma cell line stably expressing a temperature sensitive p53. Cells were exposed to ascorbic acid and glycerophosphates to hasten in vitro osteoblast differentiation and maintained either at 32 or 37 degrees C for expression of the wild type or mutant p53 phenotype. The expression of BMP-2, BMP-4 and BMP-7 were modulated in a p53 dependent fashion. We were able to confirm the p53 dependency of BMP-2 independently by RT-PCR. While BMP-2 expression was evident in the presence of both wild type and mutant p53, regulated expression was seen only in cells expressing wild type p53. Transient over expression of wild type p53 did not result in the same BMP-2 response as stable expression showing that the presence of p53 may be important for an orderly development of osteoblast differentiation rather than a direct effect on gene expression. The functional relationship between p53 and these bone specific markers is discussed.

Alternative splicing of LYT1 transcripts in Trypanosoma cruzi

As a result of alternative trans splicing, three distinct LYT1 mRNAs are produced in Trypanosoma cruzi, two encoding the full-length LYT1 protein and the third encoding a truncated LYT1 protein lacking a possible signal sequence. Analysis of the three mRNAs in different developmental forms of the parasite revealed that the alternative processing events were regulated differently during the parasite life cycle.

LYT1 protein is required for efficient in vitro infection by Trypanosoma cruzi

Trypanosoma cruzi invasion of host cells involves several discrete steps: attachment, parasite internalization mediated by recruitment and fusion of host cell lysosomes, and escape from the parasitophorous vacuole to liberate amastigotes to multiply freely in the cytosol. This report describes the initial characterization of the LYT1 gene and the demonstration that the gene product is involved in cell lysis and infectivity. Mutational analysis demonstrated that deletion of LYT1 resulted in attenuation of infection, which was associated with diminished hemolytic activity. Reintroduction of LYT1 restored infectivity in null mutants, confirming the critical role of LYT1 in infection. Additionally, in vitro stage transition experiments with LYT1-deficient lines showed that these parasites converted to extracellular amastigote-like cells and metacyclic trypomastigotes more rapidly than wild-type parasites, suggesting that the diminished infectivity was not a result of the LYT1 deficiency that affected the parasite's ability to complete the life cycle.

Characterization of the Trypanosoma cruzi Cdc2p-related protein kinase 1 and identification of three novel associating cyclins

Several Cdc2p-related protein kinases (CRKs) have been described in trypanosomatids but their role in the control of the cell cycle nor their biological functions have been addressed. In Trypanosoma cruzi two CRKs have been identified, TzCRK1 and TzCRK3. In this work we further characterize T. cruzi CRK1 and report the identification of three novel associating cyclins. We demonstrate that CRK1 levels and localization do not vary during the cell cycle, and show that it is localized in the cytoplasm, discrete regions of the nucleus, and is highly concentrated in the mitochondrion DNA (kinetoplast), suggesting a putative control function in this organelle. Using purified anti-CRK1 IgGs, we immunoprecipitated from the soluble fraction of T. cruzi epimastigote forms a protein kinase activity which is not inhibited by CDK inhibitors. In addition, we co-precipitated with p13Suc1p beads a kinase activity that was inhibited by the CDK inhibitor flavopiridol and olomoucine. Lastly, using the yeast two-hybrid system we identified three novel cyclin-like proteins able to associate with TzCRK1, and demonstrate that two of these cyclins also bind the T. cruzi CRK3 protein, indicating that these two CRKs are cyclin-dependent kinases.

Mutational analysis of 3' splice site selection during trans-splicing

trans-Splicing is essential for mRNA maturation in trypanosomatids. A conserved AG dinucleotide serves as the 3' splice acceptor site, and analysis of native processing sites suggests that selection of this site is determined according to a 5'-3' scanning model. A series of stable gene replacement lines were generated that carried point mutations at or near the 3' splice site within the intergenic region separating CUB2.65, the calmodulin-ubiquitin associated gene, and FUS1, the ubiquitin fusion gene of Trypanosoma cruzi. In one stable line, the elimination of the native 3' splice acceptor site led to the accumulation of Y-branched splicing intermediates, which served as templates for mapping the first trans-splicing branch points in T. cruzi. In other lines, point mutations shifted the position of the first consensus AG dinucleotide either upstream or downstream of the wild-type 3' splice acceptor site in this intergenic region. Consistent with the scanning model, the first AG dinucleotide downstream of the branch points was used as the predominant 3' splice acceptor site. In all of the stable lines, the point mutations affected splicing efficiency in this region.

Variation of transient gene expression within single lineages of Trypanosoma cruzi

The biodiversity of Trypanosoma cruzi is one of the main factors complicating the understanding of its molecular epidemiology. As an alternative to classical genetic methods, investigators have used DNA-mediated transformation techniques to study this diversity. Recently, transient expression data were shown to correlate with the genetic data. This led investigators to speculate on a potential speciation within clonal populations of Trypanosoma cruzi. To further test the phylogenetic significance of transient expression analysis in Trypanosoma cruzi, multiple plasmids were used to drive the expression of a reporter gene in different parasite populations. In our study, population specific expression of the reporter gene was observed but the variability revealed by these transient expression assays was very large and did not follow the grouping of Trypanosoma cruzi populations in 2 lineages. In this report, we discuss some of the limitations of transient assays on such a diverse parasite.

Hybridization mapping of Trypanosoma cruzi chromosomes III and IV

As part of the Trypanosoma Genome Initiative launched by the World Health Organization (WHO), a physical clone map of Trypanosoma cruzi chromosomes III and IV was generated to facilitate both DNA sequence analysis of the parasite's genome and the investigation of chromosome organization. Apart from a few genetic markers, anonymous cosmids were taken from chromosomal sublibraries and individually hybridized to filter arrays of the relevant cosmid library. The probe order was determined from the hybridization fingerprint results and used to define a fitting clone order, with few gaps remaining. The results were independently verified by hybridizations to a bacterial artificial chromosome (BAC) library and, in case of chromosome III, restriction mapping. For gap closure, additional experiments on a total cosmid library were carried out. The possible tiling paths consist of 26 clones for chromosome III (610 kbp) and 28 clones for chromosome IV (680 kbp).

The calmodulin-ubiquitin (CUB) genes of Trypanosoma cruzi are essential for parasite viability

The CUB genes represent single copy genes in the diploid Trypanosoma cruzi genome. In this report data are presented which demonstrate that a single expressed CUB gene is necessary for parasite viability. Although either CUB gene could be deleted individually, repeated attempts to simultaneously delete both genes were unsuccessful. The essential nature of the CUB genes was further supported by studies which demonstrated positive selection for CUB gene expression. Positive selection was demonstrated by carrying out dual gene replacements which showed that both native CUB genes could be efficiently deleted provided the CalB1 calmodulin gene was simultaneously replaced by a CUB gene protein coding sequence. Although the function of the CUB gene product remains unknown the experiments presented here indicate the product is likely to play an important role in the parasites' life cycle.

Adenovirus-mediated transfer of a gene encoding acyloxyacyl hydrolase (AOAH) into mice increases tissue and plasma AOAH activity

Although the host response to gram-negative bacterial infection follows largely from the interactions of bacterial lipopolysaccharides (LPS or endotoxin) with host cells, little information is available concerning the mechanisms by which the host eliminates or detoxifies LPS. Acyloxyacyl hydrolase (AOAH) is an enzyme, found in phagocytic cells, that catalyzes the enzymatic deacylation of the lipid A moiety of LPS. Enzymatically deacylated LPS is much less potent than LPS at inducing responses in human cells, and it can antagonize the ability of LPS to activate human macrophages, neutrophils, and endothelial cells. Despite these observations, the physiologic role of LPS deacylation remains undefined. To investigate the ability of AOAH to carry out LPS deacylation in vivo, we produced a recombinant adenovirus carrying a gene encoding (AOAH) (Ad.CMV-AOAH) and employed this vector to elicit transient overexpression of AOAH in mice. Mice infected with Ad.CMV-AOAH expressed high levels of the enzyme in plasma, liver, spleen, and kidney. Although adenovirus-induced hepatitis reduced hepatic uptake of intravenously injected [3H]LPS, animals expressing the transgene deacylated a larger fraction of the [3H]LPS taken up by their livers than did mice infected with a control adenovirus. These studies indicate that AOAH can catalyze the deacylation of LPS in vivo, and they provide evidence that the rates of hepatic LPS uptake and deacylation are not closely linked.

Expression of mammalian cytokines by Trypanosoma cruzi indicates unique signal sequence requirements and processing

A vector based upon the calmodulin-ubiquitin 2.65 locus of Trypanosoma cruzi has enabled the expression and secretion of the murine cytokines interleukin-2 (IL-2) and gamma-interferon (gamma-IFN) by transfected T. cruzi. The T. cruzi-derived cytokines were bioactive and produced by both epimastigotes and mammalian forms. The native coding sequence of IL-2 was sufficient to cause secretion of the protein, but the gamma-IFN signal sequence had to be replaced by the IL-2 signal sequence (IL-2/gamma-IFN) to allow efficient secretion of gamma-IFN. The amino acid sequences at the N-termini of the secreted T. cruzi-derived cytokines were different from the expected murine secreted protein. The secreted IL-2 was cleaved six amino acids downstream from the murine signal sequence cleavage site, and the hybrid IL-2/gamma-IFN molecule was cleaved three amino acids downstream from the predicted signal cleavage site in the IL-2/gamma-IFN molecule. These apparent differences in signal peptide sequence requirements and cleavage sites most likely indicate that the signal sequence processing in trypanosomes is distinct from that of higher eukaryotes.

Analyzing expression of the calmodulin and ubiquitin-fusion genes of Trypanosoma cruzi using simultaneous, independent dual gene replacements

We describe here a strategy for introducing simultaneous, independent gene replacements into the Trypanosoma cruzi chromosome. The goal of this study was to use two linear DNA fragments to simultaneously replace the CalA2 calmodulin and FUS1 ubiquitin-fusion genes with the neomycin resistance (neo(r)) and chloramphenicol acetyltransferase (CAT) genes, respectively. One clone (D6), of thirty G418-resistant clones analyzed, carried the desired dual gene replacement. CDNA sequence analysis indicated that the CAT mRNA was accurately trans-spliced using the previously identified FUS1 mini-exon addition site. However, DNA sequence analysis of the intergenic sequence immediately upstream of the neo(r) gene in clone D6 identified a mutation which altered the pattern of trans-splicing of the neo(r) mRNA. Possible effects of this mutation on 3' splice acceptor site selection are discussed.

Using simultaneous, tandem gene replacements to study expression of the multicopy ubiquitin-fusion (FUS) gene family of Trypanosoma cruzi

Many genes in trypanosomes exist as members of multicopy gene families. Due to this fact it is frequently difficult to determine if specific members of a gene family are expressed. We describe here a strategy for simultaneous tandem gene replacement in T. cruzi which leads to the replacement of the gene of interest by a silent reporter gene, the expression of which can be assayed in stable transformants. To determine if the FUS1 gene (one of 5 copies of the ubiquitin-fusion, FUS, gene family) was expressed, stable G418-resistant transformants were isolated in which the tandemly arrayed CUB2.65 and FUS1 genes were precisely replaced by the neomycin phosphotransferase (neo(r)) and chloramphenicol acetyltransferase (CAT) genes, respectively. All stable clones carrying the tandem gene replacements were shown to express the CAT activity indicating that FUS1 is expressed in mid-log epimastigotes. Northern blot analysis of parasites carrying the tandem gene replacements indicated that at least one other member of the FUS gene family is expressed and that there were no apparent polar effects on the expression of genes downstream of the replacement events. These experiments have demonstrated the utility of tandem gene replacements as a means of inserting a nonselected reporter gene into the chromosome, facilitating the molecular genetic analysis of the expression of multicopy gene families.

The calmodulin-ubiquitin associated genes of Trypanosoma cruzi: their identification and transcription

We describe here the identification of the calmodulin-ubiquitin associated (CUB) genes of Trypanosoma cruzi. A single CUB gene resides in a 1.5-kb DNA sequence linking the calmodulin and ubiquitin genes in the 2.65 and 2.8 loci (CUB2.65 and CUB2.8 respectively). The CUB genes also share the same coding strand as the flanking calmodulin and ubiquitin genes. DNA sequence analysis reveals that each CUB gene contains an open reading frame which would encode a protein of 208 amino acids. The CUB protein shares homology with the recently identified calcium binding EFH5 protein of T. brucei. Transcription of the CUB genes results in the generation of a mRNA of approximately 1.0 kb. CUB cDNA sequence analysis following PCR amplification of the CUB mRNA population indicates that both genes are expressed and trans-spliced, but utilize different 3' acceptor sites for the trans-splicing reaction.

Stable transformation of Trypanosoma cruzi: inactivation of the PUB12.5 polyubiquitin gene by targeted gene disruption

Analysis of gene expression in Trypanosoma cruzi has been impeded by the lack of efficient, stable, DNA-mediated transfection systems. We describe here the establishment of such a system for T. cruzi. Stable transformants were isolated following integration of the circular transforming plasmid into the chromosome by homologous recombination. Mutants with a disrupted PUB12.5 polyubiquitin gene, resulting from targeted integration of the plasmid vector, have been isolated. A mutant harboring the disrupted PUB12.5 gene lacks the intact PUB12.5 mRNA as well as transcripts corresponding to the truncated gene. Genomic Southern-blot analysis indicates that the inserted plasmid is tandemly repeated in each of the clones analyzed. A secondary recombination event in one clone resulted in a deletion within the 2.65 calmodulin-ubiquitin locus, encompassing the sequence from the CalA2 calmodulin gene to the PUB12.5 polyubiquitin gene.

Linkage of the calmodulin and ubiquitin loci in Trypanosoma cruzi

We describe here the organization of the calmodulin genes of Trypanosoma cruzi and their linkage to the ubiquitin gene family. The nucleotide sequence of the CalA2 gene has been determined and is 85% homologous to the protein coding sequence of the calmodulin genes of the African trypanosome, Trypanosoma brucei. The proteins encoded by CalA2 and the T. brucei genes contain a single mismatch out of a total of 149 amino acids. The genome of T. cruzi contains eight calmodulin genes present at two distinct loci (2.8 and 2.65) each of which is linked to downstream ubiquitin genes. Within each locus two calmodulin gene families have been defined, CalA and CalB. Each calmodulin locus consist of alternating tandem arrays of the CalA and CalB genes. Both 2.8 and 2.65 calmodulin loci and their respective downstream ubiquitin genes share the same DNA coding strand. Transcription of the calmodulin genes in the epimastigote stage of T. cruzi results in the generation of two stable mRNAs of 1.6Kb and 1.1Kb.

Purification and properties of the NusB protein of Escherichia coli

Mutations in the nusB gene of Escherichia coli block transcriptional antitermination mediated by the N gene protein of bacteriophage lambda. We describe here two methods of overproducing the NusB protein in E. coli and a method of purifying NusB to apparent homogeneity on a large scale. Purified NusB directly stimulates transcriptional antitermination by the lambda N protein in vitro. It behaves as a monomer (Mr = 15,689) during gel permeation chromatography and gradient sedimentation. The number of NusB molecules in a wild type E. coli K12 cell ranges from about 3,000 to about 6,000 molecules/cell, depending on the growth medium, and is about 50-80% of the number of molecules of the core component of RNA polymerase in the cell. This implies that NusB has a major role in regulating chain elongation during the transcription of E. coli genes. Many E. coli strains with nusB mutations cannot grow at low temperature. However, a sup+ strain with the suppressible amber mutation nusBam115 can grow at 42 degrees C. Since such a strain does not produce NusB protein detectable by immunoprecipitation with anti-NusB, normal amounts of NusB are not essential for the survival of E. coli at 42 degrees C.

The genomic organization and transcription of the ubiquitin genes of Trypanosoma cruzi

We describe here the organization of the ubiquitin genes of the parasitic protozoan Trypanosoma cruzi. T. cruzi contains greater than 100 ubiquitin coding sequences all of which are clustered into a 27 kb segment of the genome. Two types of ubiquitin coding sequences were found. There are five fusion genes (FUS1-5) consisting of a ubiquitin coding sequence fused to a basic non-ubiquitin sequence. The T. cruzi ubiquitin fusion protein is 84% homologous to the product of the UBI gene of Saccharomyces cerevisiae. The non-ubiquitin domains of the two proteins are 67% homologous. There are five polyubiquitin coding genes (PUB) each consisting of varying lengths of polyubiquitin coding sequence and terminating with a single copy of the larger fusion gene. Transcription of the ubiquitin genes results in the generation of six major poly(A)+ mRNAs. The pattern of transcription accurately reflects the genomic organization, in that the transcripts consist of either a single copy of the ubiquitin fusion coding sequence or varying lengths of polyubiquitin (up to 52 copies of the ubiquitin coding unit) each ending with a single copy of the ubiquitin fusion sequence. Finally, there are heat shock elements 5' to the PUB genes and transcription patterns are altered under conditions of stress.

The nucleotide sequence of the Escherichia coli K12 nusB (groNB) gene

The nusB (groNB) gene product of Escherichia coli plays a pivotal role in allowing bacteriophage lambda N protein to function as an antiterminator of mRNA transcription and in modulating host gene expression. In addition it is essential for bacterial viability since mutations in it result in a cold-sensitivity phenotype for growth. We have previously cloned the nusB gene and shown it to code for a 14,500-Mr protein. Here we present the primary DNA sequence of the nusB gene. From the sequence we deduce that it codes for a slightly basic protein (21 basic as opposed to 20 acidic amino acids) composed of 139 amino acids with a cumulative 15,689-Mr. The predicted N-terminal amino acid sequence as well as the overall amino acid composition agrees well with that of the purified protein.

Identification of the E. coli groNB(nusB) gene product

The E. coli groNB(nusB) gene product has been previously shown to be necessary for bacteriophage lambda N protein function. The product of the groNB gene has been identified on SDS polyacrylamide gels after infection of UV-irradiated E. coli cells with various lambda groNB+ transducing phage derivatives. It is a polypeptide with an apparent molecular weight of 14,000 daltons. Transducing phage carrying either a deletion or an amber mutation in the groNB gene fail to synthesize the 14,000-Mr polypeptide chain upon infection of a sup+ host. However, am+ revertants of the lambda groNBam phage do induce the synthesis of the polypeptide.

Studies on the E. coli groNB (nusB) gene which affects bacteriophage lambda N gene function

Escherichia coli mutants, called groNB, which block the growth of bacteriophage lambda at the level of action of the gene N product, have been isolated as survivors at 42 degrees C of bacteria carrying a) the defective prophage lambda bio11 i lambda cI857 delta H1 or b) the pcR1 plasmid containing the EcoRI immunity fragment of phage lambda cI857. In addition, groNB bacterial mutants have been isolated at 37 degrees C, as large colony formers in the presence of lambda i lambda cI h434, lambda i lambda cI h lambda, and lambda i lambda cI h80 phage. The groNB locus is located at 9 minute of the E. coli genetic map with the order of the neighboring loci being proC tsx groNB purE. Most groNB mutations isolated at 42 degrees C were found to interfere in addition with bacterial growth at low temperatures, since (a) the GroNB phenotypes of lambda growth inhibition and bacterial cold sensitivity cannot be separated by P1 transduction, and (b) some cold resistant revertants simultaneously become Gro+ for lambda growth. Lambda transducing phages carrying the groNB+ bacterial gene have been isolated. GroNB mutant bacteria lysogenized by the transducing phage acquire the Gro+ phenotype and simultaneously the cold resistant phenotype, suggesting that the groNB mutations are recessive to the wild-type gene.