Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 14 de 14
Filter
1.
Clin Cancer Res ; 29(8): 1429-1439, 2023 04 14.
Article in English | MEDLINE | ID: mdl-36652553

ABSTRACT

PURPOSE: Inhibition of monocarboxylate transporter (MCT) 1-mediated lactate transport may have cytostatic and/or cytotoxic effects on tumor cells. We report results from the dose-escalation part of a first-in-human trial of AZD3965, a first-in-class MCT1 inhibitor, in advanced cancer. PATIENTS AND METHODS: This multicentre, phase I, dose-escalation and dose-expansion trial enrolled patients with advanced solid tumors or lymphoma and no standard therapy options. Exclusion criteria included history of retinal and/or cardiac disease, due to MCT1 expression in the eye and heart. Patients received daily oral AZD3965 according to a 3+3 then rolling six design. Primary objectives were to assess safety and determine the MTD and/or recommended phase II dose (RP2D). Secondary objectives for dose escalation included measurement of pharmacokinetic and pharmacodynamic activity. Exploratory biomarkers included tumor expression of MCT1 and MCT4, functional imaging of biological impact, and metabolomics. RESULTS: During dose escalation, 40 patients received AZD3965 at 5-30 mg once daily or 10 or 15 mg twice daily. Treatment-emergent adverse events were primarily grade 1 and/or 2, most commonly electroretinogram changes (retinopathy), fatigue, anorexia, and constipation. Seven patients receiving ≥20 mg daily experienced dose-limiting toxicities (DLT): grade 3 cardiac troponin rise (n = 1), asymptomatic ocular DLTs (n = 5), and grade 3 acidosis (n = 1). Plasma pharmacokinetics demonstrated attainment of target concentrations; pharmacodynamic measurements indicated on-target activity. CONCLUSIONS: AZD3965 is tolerated at doses that produce target engagement. DLTs were on-target and primarily dose-dependent, asymptomatic, reversible ocular changes. An RP2D of 10 mg twice daily was established for use in dose expansion in cancers that generally express high MCT1/low MCT4).


Subject(s)
Antineoplastic Agents , Neoplasms , Humans , Neoplasms/drug therapy , Neoplasms/chemically induced , Pyrimidinones/pharmacology , Antineoplastic Agents/adverse effects , Thiophenes/pharmacology , Maximum Tolerated Dose , Dose-Response Relationship, Drug
2.
Br J Cancer ; 127(5): 937-947, 2022 09.
Article in English | MEDLINE | ID: mdl-35618788

ABSTRACT

BACKGROUND: We evaluated the therapeutic potential of combining the monocarboxylate transporter 1 (MCT1) inhibitor AZD3965 with the mitochondrial respiratory Complex I inhibitor IACS-010759, for the treatment of diffuse large B-cell lymphoma (DLBCL), a potential clinically actionable strategy to target tumour metabolism. METHODS: AZD3965 and IACS-010759 sensitivity were determined in DLBCL cell lines and tumour xenograft models. Lactate concentrations, oxygen consumption rate and metabolomics were examined as mechanistic endpoints. In vivo plasma concentrations of IACS-010759 in mice were determined by LC-MS to select a dose that reflected clinically attainable concentrations. RESULTS: In vitro, the combination of AZD3965 and IACS-010759 is synergistic and induces DLBCL cell death, whereas monotherapy treatments induce a cytostatic response. Significant anti-tumour activity was evident in Toledo and Farage models when the two inhibitors were administered concurrently despite limited or no effect on the growth of DLBCL xenografts as monotherapies. CONCLUSIONS: This is the first study to examine a combination of two distinct approaches to targeting tumour metabolism in DLBCL xenografts. Whilst nanomolar concentrations of either AZD3965 or IACS-010759 monotherapy demonstrate anti-proliferative activity against DLBCL cell lines in vitro, appreciable clinical activity in DLBCL patients may only be realised through their combined use.


Subject(s)
Lymphoma, Large B-Cell, Diffuse , Symporters , Animals , Apoptosis , Cell Line, Tumor , Glycolysis , Humans , Lymphoma, Large B-Cell, Diffuse/pathology , Mice , Monocarboxylic Acid Transporters , Oxidative Phosphorylation , Symporters/metabolism
4.
Trials ; 22(1): 550, 2021 Aug 19.
Article in English | MEDLINE | ID: mdl-34412682

ABSTRACT

OBJECTIVES: The primary objective is to evaluate the efficacy of camostat to prevent respiratory deterioration in patients with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection. Secondary objectives include assessment of the ability of camostat to reduce the requirement for Coronavirus disease 2019 (COVID-19) related hospital admission and to reduce the requirement for supplementary oxygen and ventilation as treatment for SARS-CoV-2 infection, to evaluate overall mortality related to COVID-19 and to evaluate the efficacy of camostat by effect on clinical improvement. Research objectives include to assess change in COVID-19 symptom severity, to evaluate the ability of camostat to reduce viral load throughout duration of illness as well as translational research on host and viral genomics, serum antibody production, COVID-19 diagnostics, and validation of laboratory testing methods and biomarkers. TRIAL DESIGN: SPIKE-1 is a randomised, multicentre, prospective, open label, community-based clinical trial. Eligible patients will be randomised 1:1 to the camostat treatment arm and control arm (best supportive care). The trial is designed to include a pilot phase recruiting up to 50 patients in each arm. An initial review at the end of the pilot phase will allow assessment of available data and inform the requirement for any protocol adaptations to include refinement of eligibility criteria to enrich the patient population and sample size calculations. Up to 289 additional patients will be randomised in the continuation phase of the trial. A formal interim analysis will be performed once 50% of the maximum sample size has been recruited PARTICIPANTS: The trial will recruit adults (≥ 18 years) who score moderate to very high risk according to COVID-age risk calculation, with typical symptoms of COVID-19 infection as per Public Health England guidance or equivalent organisations in the UK, Health Protection Scotland, Public Health Wales, Public Health Agency (Northern Ireland) and with evidence of current COVID-19 infection from a validated assay. The trial is being conducted in the UK and patients are recruited through primary care and hospital settings. INTERVENTION AND COMPARATOR: Eligible patients with be randomised to receive either camostat tablets, 200 mg four times daily (qds) for 14 days (treatment arm) or best supportive care (control arm). MAIN OUTCOMES: Primary outcome measure: the rate of hospital admissions requiring supplemental oxygen. Secondary outcome measures include: the rate of COVID-19 related hospital admission in patients with SARS-CoV-2 infection; the number of supplementary oxygen-free days and ventilator-free days measured at 28 days from randomisation; the rate of mortality related to COVID-19 one year from randomisation; the time to worst point on the nine-point category ordinal scale (recommended by the World Health Organization: Coronavirus disease (COVID-2019)) or deterioration of two points or more, within 28 days from randomisation. Research outcomes include the assessment of change in COVID-19 symptom severity on days 1-14 as measured by (1) time to apyrexia (maintained for 48 hrs) by daily self-assessment of temperature, time to improvement (by two points) in peripheral oxygenation saturation defined by daily self-assessment of fingertip peripheral oxygenation saturation levels, (3) assessment of COVID-19 symptoms using the Flu-iiQ questionnaire (determined by app recording and/or daily video call (or phone) consultation and (4) assessment of functional score (where possible) at screening, day 7 and 14. The ability of camostat to reduce viral load throughout duration of illness will be assessed by (1) change in respiratory (oropharyngeal/nasopharyngeal swab RT-PCR) log10 viral load from baseline to Days 7 and 14, (2) change in respiratory (saliva RT-PCR) log10 viral load from baseline to Days 1-14 and (3) change in upper respiratory viral shedding at Day 1 -14 measured as time to clearance of nasal SARS-CoV-2, defined as 2 consecutive negative swabs by qPCR. Additional translational research outcomes include assessment of host and viral genomics, serum antibody production and COVID-19 diagnostics at baseline and on Days 7 and 14. RANDOMISATION: Eligible patients will be randomised using an interactive web response system (IWRS) in a 1:1 ratio to one of two arms: (1) treatment arm or (2) control arm. BLINDING (MASKING): The trial is open-label. NUMBERS TO BE RANDOMISED (SAMPLE SIZE): The trial is designed to include a pilot and a continuation phase. Up to 100 patients (randomised 1:1 treatment and control arm) will be recruited in the pilot phase and a maximum of 289 patients (randomised 1:1 treatment and control) will be recruited as part of the continuation phase. The total number of patients recruited will not exceed 389. TRIAL STATUS: Protocol version number v3 25 September 2020. Trial opened to recruitment on 04 August 2020. The authors anticipate recruitment to be completed by October 2021. TRIAL REGISTRATION: EudraCT 2020-002110-41; 18 June 2020 ClinicalTrials.gov NCT04455815 ; 02 July 2020 FULL PROTOCOL: The full protocol is attached as an additional file, accessible from the Trials website (Additional file 1). Unpublished PK data provided under confidentiality agreement to the trial Sponsor has been removed from the background section of the protocol to allow for publication of the trial protocol. In the interest in expediting dissemination of this material, the familiar formatting has been eliminated; this Letter serves as a summary of the key elements of the full protocol.


Subject(s)
COVID-19 , Clinical Trials, Phase II as Topic , Clinical Trials, Phase III as Topic , Randomized Controlled Trials as Topic , Spike Glycoprotein, Coronavirus , Esters , Guanidines , Humans , Membrane Fusion , Multicenter Studies as Topic , Prospective Studies , SARS-CoV-2
5.
Sci Transl Med ; 12(571)2020 11 25.
Article in English | MEDLINE | ID: mdl-33239386

ABSTRACT

The reprogramming of a patient's immune system through genetic modification of the T cell compartment with chimeric antigen receptors (CARs) has led to durable remissions in chemotherapy-refractory B cell cancers. Targeting of solid cancers by CAR-T cells is dependent on their infiltration and expansion within the tumor microenvironment, and thus far, fewer clinical responses have been reported. Here, we report a phase 1 study (NCT02761915) in which we treated 12 children with relapsed/refractory neuroblastoma with escalating doses of second-generation GD2-directed CAR-T cells and increasing intensity of preparative lymphodepletion. Overall, no patients had objective clinical response at the evaluation point +28 days after CAR-T cell infusion using standard radiological response criteria. However, of the six patients receiving ≥108/meter2 CAR-T cells after fludarabine/cyclophosphamide conditioning, two experienced grade 2 to 3 cytokine release syndrome, and three demonstrated regression of soft tissue and bone marrow disease. This clinical activity was achieved without on-target off-tumor toxicity. Targeting neuroblastoma with GD2 CAR-T cells appears to be a valid and safe strategy but requires further modification to promote CAR-T cell longevity.


Subject(s)
Neuroblastoma , Receptors, Chimeric Antigen , Child , Humans , Immunotherapy, Adoptive , Neoplasm Recurrence, Local , Neuroblastoma/therapy , Receptors, Antigen, T-Cell/genetics , Receptors, Chimeric Antigen/genetics , T-Lymphocytes , Tumor Microenvironment
6.
Cancer Lett ; 458: 66-75, 2019 08 28.
Article in English | MEDLINE | ID: mdl-31121213

ABSTRACT

Despite the effectiveness of endocrine therapies to treat estrogen receptor-positive (ER+) breast tumours, two thirds of patients will eventually relapse due to de novo or acquired resistance to these agents. Cancer Stem-like Cells (CSCs), a rare cell population within the tumour, accumulate after anti-estrogen treatments and are likely to contribute to their failure. Here we studied the role of p21-activated kinase 4 (PAK4) as a promising target to overcome endocrine resistance and disease progression in ER + breast cancers. PAK4 predicts for resistance to tamoxifen and poor prognosis in 2 independent cohorts of ER + tumours. We observed that PAK4 strongly correlates with CSC activity in metastatic patient-derived samples irrespective of breast cancer subtype. However, PAK4-driven mammosphere-forming CSC activity increases alongside progression only in ER + metastatic samples. PAK4 activity increases in ER + models of acquired resistance to endocrine therapies. Targeting PAK4 with either CRT PAKi, a small molecule inhibitor of PAK4, or with specific siRNAs abrogates CSC activity/self-renewal in clinical samples and endocrine-resistant cells. Together, our findings establish that PAK4 regulates stemness during disease progression and that its inhibition reverses endocrine resistance in ER + breast cancers.


Subject(s)
Antineoplastic Agents, Hormonal/pharmacology , Breast Neoplasms/drug therapy , Breast Neoplasms/pathology , Neoplastic Stem Cells/pathology , Receptors, Estrogen/metabolism , Tamoxifen/pharmacology , p21-Activated Kinases/metabolism , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , Disease Progression , Down-Regulation , Drug Resistance, Neoplasm , Estrogen Receptor Antagonists/pharmacology , Female , Fulvestrant/pharmacology , Gene Expression , Humans , MCF-7 Cells , Meta-Analysis as Topic , Neoplasm Metastasis , Neoplastic Stem Cells/drug effects , Neoplastic Stem Cells/metabolism , Prognosis , Small Molecule Libraries/pharmacology , p21-Activated Kinases/antagonists & inhibitors , p21-Activated Kinases/biosynthesis , p21-Activated Kinases/genetics
7.
Cancer Lett ; 289(1): 71-80, 2010 Mar 01.
Article in English | MEDLINE | ID: mdl-19740597

ABSTRACT

We have examined expression of the Myc target gene Misu (NSUN2) in breast cancer. There was extensive copy number gain, and increased mRNA and protein levels, of Misu in approximately one third of breast cancer cell lines and primary tumours examined, irrespective of tumour subtype. Genes on 5p15.31-33, where Misu is located, showed evolutionary synteny. siRNA-mediated knockdown of Misu reduced cell number in over half of the cell lines tested, irrespective of estrogen receptor status. We conclude that Misu is up-regulated in a substantial proportion of breast cancers and has therapeutic potential as a drug target.


Subject(s)
Breast Neoplasms/genetics , Chromosomes, Human, Pair 5/genetics , Gene Dosage , Genetic Predisposition to Disease , Methyltransferases/metabolism , Blotting, Western , Cell Survival , Female , Gene Expression Profiling , Genome, Human/genetics , Humans , Methyltransferases/genetics , RNA, Messenger/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Up-Regulation
8.
J Cell Biol ; 186(1): 27-40, 2009 Jul 13.
Article in English | MEDLINE | ID: mdl-19596847

ABSTRACT

Myc-induced SUN domain-containing protein (Misu or NSun2) is a nucleolar RNA methyltransferase important for c-Myc-induced proliferation in skin, but the mechanisms by which Misu contributes to cell cycle progression are unknown. In this study, we demonstrate that Misu translocates from the nucleoli in interphase to the spindle in mitosis as an RNA-protein complex that includes 18S ribosomal RNA. Functionally, depletion of Misu caused multiple mitotic defects, including formation of unstructured spindles, multipolar spindles, and chromosome missegregation, leading to aneuploidy and cell death. The presence of both RNA and Misu is required for correct spindle assembly, and this process is independent of active translation. Misu might mediate its function at the spindle by recruiting nucleolar and spindle-associated protein (NuSAP), an essential microtubule-stabilizing and bundling protein. We further identify NuSAP as a novel direct target gene of c-Myc. Collectively, our results suggest a novel mechanism by which c-Myc promotes proliferation by stabilizing the mitotic spindle in fast-dividing cells via Misu and NuSAP.


Subject(s)
Cell Nucleolus/enzymology , Methyltransferases/metabolism , Spindle Apparatus/enzymology , Animals , Apoptosis , Cell Line, Tumor , Humans , Immunoprecipitation , Interphase , Mice , Mice, Transgenic , Microtubule-Associated Proteins , Microtubules/enzymology , Mitosis , Necrosis , Protein Binding , Protein Biosynthesis , Protein Transport , Proto-Oncogene Proteins c-myc/genetics , Proto-Oncogene Proteins c-myc/metabolism , RNA, Ribosomal, 18S/metabolism , Tubulin/metabolism
9.
J Biol Chem ; 281(49): 37353-60, 2006 Dec 08.
Article in English | MEDLINE | ID: mdl-17015441

ABSTRACT

We have investigated the glycosylation, disulfide bonding, and subunit structure of mouse TRPM8. To do this, amino-terminal c-myc or hemagglutinin epitope-tagged proteins were incorporated and expressed in Chinese hamster ovary cells. These modifications had no obvious effects on channel function in intracellular calcium imaging assays upon application of agonists, icilin or menthol, and cold temperatures. Unmodified TRPM8 migrates with an apparent mass of 129 kDa and can be glycosylated in Chinese hamster ovary cells to give glycoproteins with apparent masses of 136 and 147 kDa. We identified two potential N-linked glycosylation sites in TRPM8 (Asn-821 and Asn-934) and mutated them to show that only the site in the putative pore region at position 934 is modified and that glycosylation of this site is not absolutely necessary for cell surface expression or responsiveness to icilin, menthol, and cool temperatures. Enzymatic cleavage of the carbohydrate chains indicated that they are complex carbohydrate. The glycosylation site is flanked in the pore by two cysteine residues that we mutated, to prove that they are involved in a conserved double cysteine motif, which is essential for channel function. Mutation of either of these cysteines abolishes function and forces the formation of a non-functional complex of the size of a homodimer. The double cysteine mutant is also non-functional. Finally, we showed in Perfluoro-octanoic acid-polyacrylamide gels that TRPM8 can form a tetramer (in addition to dimer and trimer forms), consistent with current thinking that functional TRP ion channels are tetrameric.


Subject(s)
TRPM Cation Channels/chemistry , TRPM Cation Channels/metabolism , Amino Acid Motifs , Amino Acid Sequence , Amino Acid Substitution , Animals , Base Sequence , Binding Sites/genetics , CHO Cells , Cell Line , Cold Temperature , Cricetinae , Cysteine/chemistry , DNA Primers/genetics , Dimerization , Glycosylation , In Vitro Techniques , Menthol/metabolism , Mice , Models, Molecular , Molecular Sequence Data , Molecular Weight , Mutagenesis, Site-Directed , Protein Structure, Quaternary , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Sequence Homology, Amino Acid , TRPM Cation Channels/genetics
10.
Br J Pharmacol ; 144(7): 889-99, 2005 Apr.
Article in English | MEDLINE | ID: mdl-15685199

ABSTRACT

We describe the properties of a novel nonpeptide kinin B1 receptor antagonist, NVP-SAA164, and demonstrate its in vivo activity in models of inflammatory pain in transgenic mice expressing the human B1 receptor. NVP-SAA164 showed high affinity for the human B1 receptor expressed in HEK293 cells (K(i) 8 nM), and inhibited increases in intracellular calcium induced by desArg10kallidin (desArg10KD) (IC50 33 nM). While a similar high affinity was observed in monkey fibroblasts (K(i) 7.7 nM), NVP-SAA164 showed no affinity for the rat B1 receptor expressed in Cos-7 cells. In transgenic mice in which the native B1 receptor was deleted and the gene encoding the human B1 receptor was inserted (hB1 knockin, hB1-KI), hB1 receptor mRNA was induced in tissues following LPS treatment. No mRNA encoding the mouse or human B1 receptor was detected in mouse B1 receptor knockout (mB1-KO) mice following LPS treatment. Freund's complete adjuvant-induced mechanical hyperalgesia was similar in wild-type and hB(1)-KI mice, but was significantly reduced in mB1-KO animals. Mechanical hyperalgesia induced by injection of the B1 agonist desArg10KD into the contralateral paw 24 h following FCA injection was similar in wild-type and hB1-KI mice, but was absent in mB1-KO animals. Oral administration of NVP-SAA164 produced a dose-related reversal of FCA-induced mechanical hyperalgesia and desArg10KD-induced hyperalgesia in hB1-KI mice, but was inactive against inflammatory pain in wild-type mice. These data demonstrate the use of transgenic technology to investigate the in vivo efficacy of species selective agents and show that NVP-SAA164 is a novel orally active B1 receptor antagonist, providing further support for the utility of B1 receptor antagonists in inflammatory pain conditions in man.


Subject(s)
Analgesics/therapeutic use , Benzamides/therapeutic use , Bradykinin B1 Receptor Antagonists , Hyperalgesia/drug therapy , Receptor, Bradykinin B1/metabolism , Sulfonamides/therapeutic use , Administration, Oral , Analgesics/chemistry , Analgesics/pharmacology , Animals , Benzamides/chemistry , Benzamides/pharmacology , COS Cells , Cell Line , Dose-Response Relationship, Drug , Female , Gene Expression Regulation/drug effects , Gene Expression Regulation/physiology , Humans , Hyperalgesia/genetics , Hyperalgesia/metabolism , Macaca mulatta , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Rats , Receptor, Bradykinin B1/genetics , Sulfonamides/chemistry , Sulfonamides/pharmacology
11.
Biometrics ; 60(3): 812-9, 2004 Sep.
Article in English | MEDLINE | ID: mdl-15339306

ABSTRACT

Here we focus on discrimination problems where the number of predictors substantially exceeds the sample size and we propose a Bayesian variable selection approach to multinomial probit models. Our method makes use of mixture priors and Markov chain Monte Carlo techniques to select sets of variables that differ among the classes. We apply our methodology to a problem in functional genomics using gene expression profiling data. The aim of the analysis is to identify molecular signatures that characterize two different stages of rheumatoid arthritis.


Subject(s)
Models, Statistical , Oligonucleotide Array Sequence Analysis/statistics & numerical data , Arthritis, Rheumatoid/classification , Arthritis, Rheumatoid/genetics , Arthritis, Rheumatoid/physiopathology , Bayes Theorem , Biometry , Humans , Markov Chains , Models, Biological , Monte Carlo Method
12.
Comb Chem High Throughput Screen ; 7(3): 231-8, 2004 May.
Article in English | MEDLINE | ID: mdl-15134529

ABSTRACT

The development of Functional Genomics technologies has opened new avenues to investigate the complexity of the immune system. Microarray technology has been particularly successful because of its relatively low cost and high genome coverage. Consequently to our ability to monitor the expression of a significant proportion of an organism genome, our understanding of the molecular dynamics behind cell differentiation and cell response has greatly improved. Molecular signatures associated to immune cells have provided important tools to investigate the molecular basis of diseases and have been often associated to diagnostic and prognostic markers. The availability of such large collection of data has stimulated the application of complex machine learning techniques in the attempt to link molecular signatures and cell physiology. Here we review the most recent developments in the analysis of molecular signatures in the immune system.


Subject(s)
Computational Biology , Genomics , Immune System/chemistry , Animals , Autoimmune Diseases/immunology , Gene Expression Profiling , Humans , Immune System/immunology , Immune System/ultrastructure , Inflammation/immunology , Leukemia/immunology , Lymphocytes/immunology , Lymphocytes/metabolism , Principal Component Analysis , Protein Array Analysis , Stem Cells/immunology , Stem Cells/metabolism , Stromal Cells/immunology , Stromal Cells/metabolism
13.
Cell ; 108(5): 705-15, 2002 Mar 08.
Article in English | MEDLINE | ID: mdl-11893340

ABSTRACT

A distinct subset of sensory neurons are thought to directly sense changes in thermal energy through their termini in the skin. Very little is known about the molecules that mediate thermoreception by these neurons. Vanilloid Receptor 1 (VR1), a member of the TRP family of channels, is activated by noxious heat. Here we describe the cloning and characterization of TRPM8, a distant relative of VR1. TRPM8 is specifically expressed in a subset of pain- and temperature-sensing neurons. Cells overexpressing the TRPM8 channel can be activated by cold temperatures and by a cooling agent, menthol. Our identification of a cold-sensing TRP channel in a distinct subpopulation of sensory neurons implicates an expanded role for this family of ion channels in somatic sensory detection.


Subject(s)
Calcium Channels/metabolism , Cold Temperature , Menthol/pharmacology , Neurons, Afferent/drug effects , Neurons, Afferent/metabolism , Thermoreceptors/metabolism , Amino Acid Sequence , Animals , Antipruritics/pharmacology , CHO Cells , Calcium/metabolism , Calcium Channels/classification , Calcium Channels/genetics , Cloning, Molecular , Cricetinae , Humans , In Situ Hybridization , Mice , Molecular Sequence Data , Patch-Clamp Techniques , Phylogeny , Sequence Alignment , TRPC Cation Channels , Tissue Distribution
14.
J Mol Biol ; 315(4): 541-9, 2002 Jan 25.
Article in English | MEDLINE | ID: mdl-11812128

ABSTRACT

In the immune state bacteriophage P4 prevents expression of the replication functions by premature termination of transcription. A small RNA, the CI RNA, is the trans acting factor that regulates P4 immunity, by pairing to complementary target sequences and causing premature transcription termination. The CI RNA is matured by RNAse P and PNPase from the leader region of the same operon it regulates. In this work we better characterize this molecule. CI RNA copy number was determined to be around 500 molecules per lysogenic cell. By S(1) mapping we defined the 3'-end at 8423(+/-1); thus CI RNA is 79(+/-1) nt long. The minimum region for correct processing requires two bases upstream of the CI RNA 5'-end and the CCA sequence at the 3'-end. Computer analysis by FOLD RNA of CI RNA sequence predicts a cloverleaf-like structure formed by a double-stranded stalk, a minor and a major stem loop, and a single-stranded bulge. We analysed several cI mutations, which fall either in the single or double-stranded CI RNA regions. Base substitutions in the main loop and in the single-stranded bulge apparently did not change CI RNA structure, but affected its activity by altering the complementarity with the target sequences, whereas a mutation in the secondary stem had a disruptive effect on CI RNA secondary structure. The effects of this latter mutation were suppressed by a base substitution that restored the complementarity with the corresponding base in the stem. Base substitutions in the main stem caused only local alterations in the secondary structure of CI. However, when the substitutions concerned either G8501 or its complementary base at the bottom of the stem, CI RNA was not correctly processed.


Subject(s)
Coliphages/genetics , Coliphages/immunology , Nucleic Acid Conformation , RNA, Antisense/chemistry , RNA, Antisense/metabolism , Base Sequence , Gene Dosage , Genes, Viral/genetics , Lysogeny , Molecular Sequence Data , Mutation/genetics , Nuclease Protection Assays , Phenotype , RNA Processing, Post-Transcriptional , RNA, Antisense/biosynthesis , RNA, Antisense/genetics , RNA, Viral/biosynthesis , RNA, Viral/chemistry , RNA, Viral/genetics , RNA, Viral/metabolism , Software , Structure-Activity Relationship , Transcription, Genetic
SELECTION OF CITATIONS
SEARCH DETAIL
...