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M R Green

Publications and source records attributed to M R Green.

At least 163 records · Page 9Linked to original sources
PubMed1994

Activator-induced conformational change in general transcription factor TFIIB.

Transcriptional activator proteins (activators) function, at least in part, by increasing preinitiation complex assembly (for reviews see refs 1-4). Previous studies have shown that an acidic activator forms a contact with the general transcription factor TFIIB (refs 5-7) and recruits it into the preinitiation complex. Mutational studies indicate that this interaction between the acidic activator and TFIIB is required for transcriptional stimulation. We show here that the acidic activator-TFIIB interaction has an additional function in preinitiation complex assembly. We provide evidence that in native TFIIB the amino- and carboxy-terminal domains are engaged in an intramolecular interaction. The acidic activator disrupts this intramolecular interaction to expose binding sites for general transcription factors that enter the preinitiation complex through association with TFIIB. Thus, the acidic activator induces a conformational change in TFIIB that drives preinitiation complex assembly forward.

Glutathione Transferase↗
PubMed1994

Yeast TAFIIS in a multisubunit complex required for activated transcription.

In higher eukaryotes the RNA polymerase II transcription factor TFIID is composed of a TATA-box-binding protein (TBP) and a set of tightly bound polypeptides, designated TBP-associated factors (TAFIIS). One or more TAFIIS are coactivators that are required for activated but not basal transcription. The eukaryotic transcription machinery is highly conserved and it is therefore puzzling that TAFIIS have not been identified in yeast. Here we use TBP as a protein-affinity ligand to isolate from yeast a multisubunit complex that is required specifically for activated transcription by RNA polymerase II. Microsequence analysis and cloning of two subunits of this complex reveal that they are the homologues of known mammalian and Drosophila TAFIIS. The genes encoding these two yeast TAFIIS are essential, suggesting that activated transcription is required for viability of Saccharomyces cerevisiae.

Amino Acid Sequence↗
PubMed1994

Nucleosome disruption and enhancement of activator binding by a human SW1/SNF complex.

CHROMATIN structure can affect the transcriptional activity of eukaryotic structural genes by blocking access of sequence-specific activator proteins (activators) to their promoter-binding sites. For example, the DNA-binding domain of the yeast GAL4 protein interacts very poorly with nucleosome cores compared with naked DNA2 (and see below), and binding of other activators is even more strongly inhibited. The way in which activators bind to nucleosomal DNA is therefore a critical aspect of transcriptional activation. Genetic studies have suggested that the multi-component SWI/SNF complex of Saccharomyces cerevisiae facilitates transcription by altering the structure of the chromatin. Here we identify and partially purify a human homologue of the yeast SWI/SNF complex (hSWI/SNF complex). We show that a partially purified hSWI/SNF complex mediates the ATP-dependent disruption of a nucleosome, thereby enabling the activators, GAL4-VP16 and GAL4-AH, to bind within a nucleosome core. We conclude that the hSWI/SNF complex acts directly to reorganize chromatin structure so as to facilitate binding of transcription factors.

Adenosine Triphosphatases↗
PubMed1994

Facilitated binding of TATA-binding protein to nucleosomal DNA.

BINDING of the TATA-binding protein (TBP) to the TATA box is required for transcription from many eukaryotic promoters in gene expression. Regulation of this binding is therefore likely to be an important determinant of promoter activity. Incorporation of the TATA sequence into nucleosomes dramatically reduces transcription initiation, presumably because of stereochemical constraints on binding of general transcription factors. Biochemical and genetic studies imply that cellular factors such as yeast SWI/SNF are required for activator function and might alter chromatin structure. One step that could be regulated during the activation process is TBP binding in chromatin 12, 13. We show here that binding of TBP to the TATA sequence is severely inhibited by incorporation of this sequence into a nucleosome. Inhibition can be overcome by ATP-dependent alterations in nucleosomal DNA structure mediated by hSWI/SNF, a putative human homologue of the yeast SWI/SNF complex. Additionally, the orientation of the TATA sequence relative to the surface of the histone core affects the access of TBP. We propose that the dynamic remodelling of chromatin structure to allow TBP binding is a key step in the regulation of eukaryotic gene expression.

Adenosine Triphosphatases↗
PubMed1994

Alternating irradiation and chemotherapy in stage III A and B nonsmall cell lung cancer: report of a cancer and Leukemia Group B phase II study 8636.

PURPOSE: A pilot trial testing the feasibility of chemotherapy and radiotherapy was done in Stage III A and B nonsmall cell lung cancer. The schedule was designed to be consistent with the laboratory model of Looney and Hopkins. METHODS AND MATERIALS: Treatment began with thrice-per-day radiotherapy for 3 days (16.2 Gy/nine fractions), followed by chemotherapy (cis-platinum 100 mg/m2 day 10, and vinblastine 4 mg/m2 days 10 and 12). A second cycle started on day 22, a third on day 43, and a fourth on day 64. We treated three cohorts. The first cohort received three cycles of radiotherapy alone, (48.6 Gy). The second cohort received three completed cycles, and the third received three completed cycles and a fourth radiotherapy course (64.8 Gy). Patients were evaluated for toxicity, protocol compliance, response, and survival. RESULTS: The patients in the first cohort experienced no toxicity. Fifty-six percent (56%) of the patients treated in cohort 2 experienced severe or life-threatening myelosuppression as did 82% of those in cohort 3. Nonhematologic toxicity was not severe; one case of Grade 3 esophagitis, one of reversible adult respiratory distress syndrome, and one radiation pneumonitis. We closed the trial after accrual to the third cohort because of significant myelosuppression. CONCLUSION: This schedule is too myelosuppressive to be used without modification.

Aged↗
PubMed1994

Nuclear protein CBP is a coactivator for the transcription factor CREB.

The transcription factor CREB binds to a DNA element known as the cAMP-regulated enhancer (CRE). CREB is activated through phosphorylation by protein kinase A (PKA), but precisely how phosphorylation stimulates CREB function is unknown. One model is that phosphorylation may allow the recruitment of coactivators which then interact with basal transcription factors. We have previously identified a nuclear protein of M(r)265K, CBP, that binds specifically to the PKA-phosphorylated form of CREB. We have used fluorescence anisotropy measurements to define the equilibrium binding parameters of the phosphoCREB:CBP interaction and report here that CBP can activate transcription through a region in its carboxy terminus. The activation domain of CBP interacts with the basal transcription factor TFIIB through a domain that is conserved in the yeast coactivator ADA-1 (ref. 8). Consistent with its role as a coactivator, CBP augments the activity of phosphorylated CREB to activate transcription of cAMP-responsive genes.

Animals↗
PubMed1994

Promoter targeting by adenovirus E1a through interaction with different cellular DNA-binding domains.

A puzzling property of the transcriptional activators encoded by several animal viruses is their ability to function promiscuously. The adenovirus E1a protein, for example, stimulates transcription of adenoviral genes as well as a wide variety of other viral and cellular genes. We show that E1a can interact with several classes of cellular DNA-binding domains and thereby be recruited to diverse promoters. Our results explain how a single protein can regulate transcription of multiple genes that lack a common promoter element.

Activating Transcription Factor 2↗
PubMed1994

Modeling eukaryotic transcriptional activation.

In recent years, many components involved in promoter-specific transcriptional activation in eukaryotes have been identified and characterized. We argue that a proper understanding of transcriptional activation will require quantitative modeling and we outline some of the considerations that such modeling will need to take into account.

Animals↗
PubMed1994

Phase II trial of gemcitabine (2,2'-difluorodeoxycytidine) in patients with adenocarcinoma of the pancreas.

Gemcitabine is a novel nucleoside analog which demonstrated a broad spectrum of preclinical activity in solid tumor models, and responses in patients with pancreas cancer during phase I evaluation. Patients with measurable adenocarcinoma of the pancreas who had received no previous chemotherapy were eligible for this multicenter phase II clinical trial. Gemcitabine 800 mg/m2 was administered intravenously weekly for 3 consecutive weeks, followed by one week rest, every 4 weeks. Forty-four patients entered the trial; 35 had at least 2 cycles of therapy. Partial response was observed in 5 patients (11%, estimated 95% confidence interval 2-20%), with a median duration of 13 months. All responding patients had stabilization or improvement in performance status. Fourteen patients had stable disease of 4 or more months. The median WBC nadir was 3.8 x 10(3)/microliters (range 1.6-9.3) and the median absolute neutrophil (ANC) nadir was 2.0 x 10(3)/microliters (range 0.4-7.2). Thrombocytopenia - 100.0 x 10(3)/microliters was observed in 15 patients; the median platelet nadir was 123.0 (range 30.0-245.0). All patients experienced a mild to moderate flu-like syndrome. In addition, one patient had a mild hemolytic-uremic syndrome which appeared related to gemcitabine therapy. Gemicitabine demonstrated marginal activity in this resistant neoplasm, without excessive toxicity. Further evaluation, including the use of more intense dosing and/or combination therapy, is warranted.

Adenocarcinoma↗
PubMed1994

Does adjuvant chemotherapy decrease distant metastasis formation in patients with non-small cell lung cancer?

Disseminated micrometastatic disease limits the effectiveness of even the most aggressive locoregional treatment strategies in patients with early stage non-small cell lung cancer. One trial of the Lung Cancer Study Group (LCSG) demonstrated a significant decrease in the hazard rate for distant recurrence produced by adjuvant CAP chemotherapy after surgical resection and radiation therapy. French investigators found a significant decrease in distant metastases formation following sequential chemotherapy, radiation, and then additional chemotherapy compared to radiation alone in patients with stage III disease. However, other completed trials are either inconclusive, incompletely analyzed thus far or show no evidence of an effect of adjuvant chemotherapy on distant metastases. Additional data from recently completed or current trials will hopefully clarify the impact of adjuvant chemotherapy on distant micrometastases in patients with potentially curable non-small cell lung cancer (NSCLC).

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

The role of induction chemotherapy before radiation therapy in non-operative management of stage III NSCLC.

Radiation therapy alone has been 'standard' management of patients with Stage III non-small cell lung cancer for several decades. Palliative benefits are routinely achieved but significant survival benefits have not been documented. Patterns of failure in Stage III patients emphasize the need to pursue better treatment for both local macroscopic disease and distant micrometastatic sites. Improved control in both areas will be necessary to meaningfully enhance outcome for the universe of Stage III NSCLC patients. Several randomized trials show a significant survival benefit when cisplatin-containing induction chemotherapy is administered prior to locoregional treatment. In the favorable subset of Stage III patients selected for study by CALGB, the surviving fraction at 2-5 years post-therapy was > or = 2-fold larger in the chemoradiation group than in the cohort treated with radiation alone. The French trial documented a significant decrease in distant metastases rate among the chemotherapy treated patients. In all the trials where patterns of failure are discussed, local disease persistence is the overwhelming rule. Future trials must evaluate improved induction chemotherapy approaches. Stage III patients are an ethical population in which to test induction therapy with new drug combinations randomized against already 'active' regimens for comparative efficacy. End points would be initial response rates, patterns of failure, and overall survival. The feasibility of high-dose chemotherapy regimens with growth factor and hematopoietic support followed by aggressive radiation must be tested. If feasible, trials randomizing high dose versus conventional dose induction programs within the context of sequential multimodality therapy should follow. Intensified radiation approaches such as hyperfractionation or CHART should be paired with active concurrent chemotherapy following induction chemotherapy alone. Pursuit of these approaches over the next several years will hopefully produce major improvements in treatment efficacy and lead to enhanced survival expectations for the large group of patients worldwide with Stage III NSCLC.

Carcinoma, Non-Small-Cell Lung↗
PubMed1994

DNA-binding domains: targets for viral and cellular regulators.

Specific DNA binding by eukaryotic transcription factors is conferred by several types of sequence motif. These domains have been extensively studied with regard to their precise interaction with DNA and the basis of sequence specificity. Evidence is accumulating that DNA-binding domains serve functions in addition to binding DNA: they are also targets of viral and cellular regulatory proteins.

Animals↗
PubMed1994

A phase II study of recombinant beta-interferon at maximum tolerated dose in patients with advanced non-small cell lung cancer: a cancer and leukemia group B study.

Forty-one patients with advanced non-small cell lung cancer (NSCLC) were entered into a phase II study of high dose recombinant interferon (rIFN)-beta. Patients received intravenous (i.v.) rIFN-beta on a Monday, Wednesday, Friday schedule with a weekly dose escalation until > or = grade 3 toxicity or 720 x 10(6) IU/dose was achieved. Thirty-eight patients were eligible. Seventeen patients received the highest planned dose of rIFN-beta and 11 experienced dose-limiting toxicity at lower doses. Ten patients developed progressive disease before grade 3 toxicity was reached. There were no objective responses observed. Significant and dose-limiting toxicities included nausea and vomiting, fever, rigors, severe dyspnea, hypotension, and hypertension. IFN-beta has no measurable antitumor activity against NSCLC even at maximum tolerated doses (MTDs).

Adult↗
PubMed1994

Human transcription factor YY1 represses human immunodeficiency virus type 1 transcription and virion production.

The transcriptional activity of human immunodeficiency virus type 1 (HIV-1) is affected by many cellular factors. Homologies near the HIV-1 initiator region to the DNA-binding sequences of YY1, a multifunctional transcription factor known to regulate diverse viral and cellular promoters, suggested that YY1 might regulate HIV-1. Antibody to YY1 blocked the formation of complexes by HeLa cell nuclear extract and a DNA oligonucleotide encoding the HIV-1 initiator region. HIV-1 long terminal repeat (LTR) expression, as measured the expression of a transfected LTR-CAT reporter gene, was repressed more than 12-fold by the cotransfection of a YY1 expression vector. HIV-1 production by both COS-1 and CEM cells after transfection of an infectious molecular HIV-1 clone was repressed 7- to 20-fold by cotransfection of a YY1 expression vector. HIV-1 production was also decreased threefold in a CD4-positive lymphocyte cell line chronically infected with HIV-1 (8E5) after transfection of YY1. In situ hybridization studies confirmed that YY1 reduced HIV-1 RNA expression. YY1 may play an important role in the regulation of HIV-1 LTR expression in vivo and virus production by infected cells.

Animals↗