Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.10.1 (ERK)
 95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The binding of lipophilic hormones, retinoids and vitamins to members of the nuclear-receptor superfamily modifies the DNA-binding and transcriptional properties of these receptors, resulting in the activation or repression of target genes. Ligand binding induces conformational changes in nuclear receptors and promotes their association with a diverse group of nuclear proteins, including SRC-1/p160, TIF-2/GRIP-1 and CBP/p300 which function as co-activators of transcription, and RIP-140, TIF-1 and TRIP-1/SUG-1 whose functions are unclear. Here we report that a short sequence motif LXXLL (where L is leucine and X is any amino acid) present in RIP-140, SRC-1 and CBP is necessary and sufficient to mediate the binding of these proteins to liganded nuclear receptors. We show that the ability of SRC-1 to bind the oestrogen receptor and enhance its transcriptional activity is dependent upon the integrity of the LXXLL motifs and on key hydrophobic residues in a conserved helix (helix 12) of the oestrogen receptor that are required for its ligand-induced activation function. We propose that the LXXLL motif is a signature sequence that facilitates the interaction of different proteins with nuclear receptors, and is thus a defining feature of a new family of nuclear proteins.
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PMID:A signature motif in transcriptional co-activators mediates binding to nuclear receptors. 919 83

The retinoblastoma susceptibility gene product pRb restricts cellular proliferation by affecting gene expression by all three classes of nuclear RNA polymerases. To elucidate the molecular mechanisms underlying pRb-mediated repression of ribosomal DNA (rDNA) transcription by RNA polymerase I, we have analyzed the effect of pRb in a reconstituted transcription system. We demonstrate that pRb, but not the related protein p107, acts as a transcriptional repressor by interfering with the assembly of transcription initiation complexes. The HMG box-containing transcription factor UBF is the main target for pRb-induced transcriptional repression. UBF and pRb form in vitro complexes involving the C-terminal part of pRb and HMG boxes 1 and 2 of UBF. We show that the interactions between UBF and TIF-IB and between UBF and RNA polymerase I, respectively, are not perturbed by pRb. However, the DNA binding activity of UBF to both synthetic cruciform DNA and the rDNA promoter is severely impaired in the presence of pRb. These studies reveal another mechanism by which pRb suppresses cell proliferation, namely, by direct inhibition of cellular rRNA synthesis.
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PMID:Mechanism of repression of RNA polymerase I transcription by the retinoblastoma protein. 923 80

The estrogen receptor (ER) belongs to a large family of nuclear receptors, many of whose members function as ligand-dependent transcriptional activators. The mechanism by which the receptor is converted from an inactive into an activated state is not yet completely understood. To investigate the kind of changes in receptor conformation and interactions that are involved in this activation, we have used the wild type ER and a set of constitutively active ER point mutants that show from 20% to nearly 100% activity in the absence of estrogen. These mutants are of particular interest as they could mimic, in the absence of ligand, the activated state of the wild type receptor. We have analyzed several transcriptional steps that could be involved in the activation: the ability of these receptors 1) to interact with several coactivators (steroid receptor coactivator-1, SRC-1; transcription intermediary factor-1, TIF-1; and estrogen receptor-associated protein 140, ERAP 140) and with members of the preinitiation complex [TATA box-binding protein (TBP), transcription factor IIB (TFIIB)]; 2) to exhibit conformational changes revealed by proteolytic digest patterns similar to those observed for the wild type hormone-occupied ER; and 3) to bend estrogen response element-containing DNA, which is thought to be one of the important phenomena triggering transcriptional activation. Our results demonstrate that the interaction of these mutant receptors with coactivators is likely to be one of the features of the activated step, as the mutant receptors interacted with some coactivators in a ligand-independent manner in proportion to their extent of constitutive activity. However, the different degrees of ligand-independent interaction of the mutant ERs with the three coactivators suggest that SRC-1, TIF-1, and ERAP 140 may play different roles in receptor activity. Limited proteolytic digest experiments reveal that the activated state of the receptor corresponds to a particular conformation of the receptor, which is fully observed with the mutant ER showing the highest activity in the absence of estrogen. Finally, it appears that in inactive or active states, the receptor exhibits distinctly different DNA-bending abilities. Addition of estradiol is able to modify the bending ability of only the wild type receptor, whereas estradiol has no influence on the constitutive receptors, which exhibited the same bending ability as that observed for the ligand-occupied wild type receptor. These data document that the ER undergoes major changes in its conformation and also in its functional properties when it is turned from an inactive into an active state and that mutational changes in the ER protein that result in constitutive, hormone-independent activation mimic many of the changes in ER properties that are normally under hormone regulation.
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PMID:Mechanistic aspects of estrogen receptor activation probed with constitutively active estrogen receptors: correlations with DNA and coregulator interactions and receptor conformational changes. 925 27

In the research field of nuclear receptors, the studies on the protein factors which interact with the steroid hormone receptors and regulate the transcriptional activity, and on the alpha and beta isoforms of glucocorticoid receptor have been in great progress. The include "intermediary Factors" such as RIP140, TIF-1, for the AF-2 which contribute to ligand-dependent transactivation function of the receptors. ARA70 which specifically interacts with androgen receptor was also cloned recently. Informations obtained from steroid hormone receptor knockout-mice experiments can also be available for the estrogen, glucocorticoid, and progesterone receptors. Furthermore, there have been more than sixty orphan receptors identified in these eight years, including HNF, Ad4BP, DAX-1, and nur77/NGFIB, some of which are mutation target genes of human congenital diseases.
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PMID:[Recent progress in the research field of nuclear receptors]. 928 39

Acanthamoeba castellanii transcription initiation factor-IB (TIF-IB) is the TATA-binding protein-containing transcription factor that binds the rRNA promoter to form the committed complex. Minor groove-specific drugs inhibit TIF-IB binding, with higher concentrations needed to disrupt preformed complexes because of drug exclusion by bound TIF-IB. TIF-IB/DNA interactions were mapped by hydroxyl radical and uranyl nitrate footprinting. TIF-IB contacts four minor grooves in its binding site. TIF-IB and DNA wrap around each other in a right-handed superhelix of high pitch, so the upstream and downstream contacts are on opposite faces of the helix. Dimethyl sulfate protection assays revealed limited contact with a few guanines in the major groove. This detailed analysis suggests significant DNA conformation dependence of the interaction.
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PMID:The fundamental ribosomal RNA transcription initiation factor-IB (TIF-IB, SL1, factor D) binds to the rRNA core promoter primarily by minor groove contacts. 936 Oct 4

CR1 elements are a family of retroposons. They are classified as long interspersed elements (LINEs) or non-long-terminal-repeat (non-LTR) retrotransposons, and they have been found in the genomes of many vertebrates. However, they have been only partially characterized, and only a 2-kb region of the 3' end of chicken CR1 has been sequenced. In the present study, we determined the entire consensus sequence of CR1 elements in the turtle genome, designated PsCR1. The first open reading frame (ORF1) of PsCR1 has two unusual arrangements of Cys residues. One of them includes a zinc finger motif, CX2CX14CX2C. The putative zinc finger has cysteine residues with identical spacing and a similar amino acid composition to those found in the species-specific transcription initiation factors SL1 and TIF-IB. The 5' untranslated region (5' UTR) of PsCR1 contains a sequence similar to part of the human L1 promoter, L1 site A, and several cis elements of the type found in eukaryotic genes. Within a region of about 500 bp, there are nine "E boxes," cis elements that are recognized by the basic helix-loop-helix (bHLH) family of proteins. This observation raises the possibility that cellular transcription factors that bind to these sequences might act in concert to regulate the expression of PsCR1. The extent of the sequence divergence of the 3' UTR of CR1 between species was found to be lower than the rate of nonsynonymous substitutions per site in ORF2, suggesting that a strict functional constraint must exist for this region. This result strongly suggests that the conserved 3'-end sequence of CR1 is the recognition site for the reverse transcriptase of CR1. A discussion is presented of a possible mechanism for the integration of CR1 elements and also of the intriguing possible recruitment of the reverse transcriptase for the retroposition of SINEs.
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PMID:Determination of the entire sequence of turtle CR1: the first open reading frame of the turtle CR1 element encodes a protein with a novel zinc finger motif. 940 32

Herpes simplex virus type 1(HSV-1) L-particles are known to be composed mainly of envelope and tegument proteins, to lack the nucleocapsid, and to be noninfectious. Thus L-particles represent interesting vaccine candidates. L-particles at > 1000/cell interfered with HSV-1 virion adsorption and penetration While L-particles did not affect HSV-1 growth kinetics in resting or nonresting BHK cultures infected with purified virions, treatment with L-particles before, or after, transfection with HSV-1 DNA resulted in a progressive increase in plaque numbers (five- to sixfold at 1000 L-particles/cell). Transfection assays using HSV-1 ts mutant DNA (ts 1201) revealed that enhancement was due to induction of otherwise nonreplicating genomes. The enhancement obtained with L-particles produced by WT HSV-1 or by mutants that are either deleted, or defective, in certain gene products was compared. Most important were the Vmw110 (ICP0) and Vmw65 (alpha-TIF) proteins, but VP11/12, VP13/14, and vhs also have a role. The L-particle-associated Vmw175 (ICP 4) protein did not appear be involved. The effect of homologous and heterologous combinations of pseudorabies virus, equineherpesvirus-1, and HSV-1 DNA's and L-particles was investigated in transfection assays. The L-particles of each virus, to varying extent, enhanced the plaquing efficiency of their own DNA but were also effective in heterologous combinations.
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PMID:The effect of herpes simplex virus type 1 L-particles on virus entry, replication, and the infectivity of naked herpesvirus DNA. 943 28

Transcription initiation of ribosomal RNA genes requires RNA polymerase I (Pol I) and auxiliary factors which either bind directly to the rDNA promoter, e.g. TIF-IB/SL1 and UBF, or are assembled into productive transcription initiation complexes via interaction with Pol I, e.g. TIF-IA, and TIF-IC. Here we show that all components required for specific rDNA transcription initiation are capable of physical interaction with Pol I in the absence of DNA and can be co-immunoprecipitated with antibodies against defined subunits of murine Pol I. Sucrose gradient centrifugation and fractionation on gel filtration columns reveals that approximately 10% of cellular Pol I elutes as a defined complex with an apparent molecular mass of > 2000 kDa. The large Pol I complex contains saturating levels of TIF-IA, TIF-IB and UBF, but limiting amounts of TIF-IC. In support of the existence of a functional complex between Pol I and basal factors, the large complex is transcriptionally active after complementation with TIF-IC. The results suggest that, analogous to class II gene transcription, a pre-assembled complex, the "Pol I holoenzyme", exists that appears to be the initiation-competent form of Pol I.
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PMID:Mammalian RNA polymerase I exists as a holoenzyme with associated basal transcription factors. 945 38

To explore the effects BICP0 (a principal transactivator of BHV-1 gene expression) on viral promoter elements, we established a cell line in which the expression of BICP0 is regulated by tetracycline. A hybrid promoter containing reiterated copies of the tet-operator (tet-O) and a minimal herpesviral alpha gene transinducing factor (alpha TIF) responsive element (minimal human cytomegalovirus immediate early promoter) was fused to the BICP0 gene and used to transform a HeLa cell line which expressed a fusion protein consisting of the repressor of the tet-O and the transactivating domain of alpha TIF. Simultaneously, the hygromycin resistance gene was transfected to select cells in media containing either hygromycin alone or both hygromycin and tetracycline. Immunofluorescent assays indicated that BICP0 was synthesised in the transformed cell lines solely upon induction of the gene by tetracycline removal. Only cells which had been kept constantly in medium containing tetracycline were able to synthesise BICP0 upon induction. Induced cell lines transactivated the native BICP0 promoter as well as the herpes simplex virus thymidine kinase promoter and the long terminal repeat sequences of human immunodeficiency virus in a dose dependent manner. These cell lines may help to further explore the functions of BICP0 as well as to investigate the molecular basis of interactions between herpes- and retroviruses.
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PMID:Construction and characterization of a stably transformed HeLa cell line in which the expression of bovine herpesvirus 1 ICP0 (BICP0) is induced by tetracycline. 958 95

Evaluation of cell morphology by bright field microscopy is the pillar of histopathological diagnosis. The need for quantitative and objective parameters for diagnosis gave rise to the development of morphometric methods. Morphometry combined with spectral imaging provides multi-pixel information from a specimen, which can be used for further image processing and quantitative analysis. The spectroscopic analysis is based on the ability of a stained histological specimen to absorb, reflect, or emit photons in ways characteristic to its interactions with specific dyes. Spectral information obtained from a histological specimen is stored in a cube whose appellate signifies the two spatial dimensions of a flat sample (x and y) and the third dimension, the spectrum, representing the light intensity for every wavelength. By mathematical analysis of the cube database, it is possible to perform the function of spectral-similarity mapping (SSM) which enables the demarcation of areas occupied by the same type of material. Spectral similarity mapping constructs new images of the specimen, revealing areas with similar stain-macromolecule characteristics and enhancing subcellular features. Spectral imaging combined with SSM reveals nuclear organization and identifies specifically the nucleoli domains. Therefore, differentiation stages as well as apoptotic and necrotic conditions are easily quantified. The commercial SpectraCube system was developed for the application of spectral imaging in biology, recording both transmitted light and fluorescence. The SKY technique utilizes the advantages of the SpectraCube for multi probe FISH and chromosome karyotyping, identifying marker chromosomes, detecting subtle chromosome translocations and clarifying complex karyotypes.
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PMID:Spectral imaging for quantitative histology and cytogenetics. 969 Jan 46


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