Search results for "binding proteins"
showing 10 items of 911 documents
Pigment Binding, Fluorescence Properties, and Oligomerization Behavior of Lhca5, a Novel Light-harvesting Protein
2005
A new potential light-harvesting protein, named Lhca5, was recently detected in higher plants. Because of the low amount of Lhca5 in thylakoid membranes, the isolation of a native Lhca5 pigment-protein complex has not been achieved to date. Therefore, we used in vitro reconstitution to analyze whether Lhca5 binds pigments and is actually an additional light-harvesting protein. By this approach we could demonstrate that Lhca5 binds pigments in a unique stoichiometry. Analyses of pigment requirements for light-harvesting complex formation by Lhca5 revealed that chlorophyll b is the only indispensable pigment. Fluorescence measurements showed that ligated chlorophylls and carotenoids are arran…
Amino acids in the second transmembrane helix of the Lhca4 subunit are important for formation of stable heterodimeric light-harvesting complex LHCI-…
2007
Photosynthetic light-harvesting complexes (LHCs) are assembled from apoproteins (Lhc proteins) and non-covalently attached pigments. Despite a considerable amino acid sequence identity, these proteins differ in their oligomerization behavior. To identify the amino acid residues determining the heterodimerization of Lhca1 and Lhca4 to form LHCI-730, we mutated the poorly conserved second transmembrane helix of the two subunits. Mutated genes were expressed in Escherichia coli and the resultant proteins were refolded in vitro and subsequently analyzed by gel electrophoresis. Replacement of the entire second helix in Lhca4 by the one of Lhca3 abolished heterodimerization, whereas it had no eff…
TFIIH Operates through an Expanded Proximal Promoter To Fine-Tune c-myc Expression
2004
A continuous stream of activating and repressing signals is processed by the transcription complex paused at the promoter of the c-myc proto-oncogene. The general transcription factor IIH (TFIIH) is held at promoters prior to promoter escape and so is well situated to channel the input of activators and repressors to modulate c-myc expression. We have compared cells expressing only a mutated p89 (xeroderma pigmentosum complementation group B [XPB]), the largest TFIIH subunit, with the same cells functionally complemented with the wild-type protein (XPB/wt-p89). Here, we show structural, compositional, and functional differences in transcription complexes between XPB and XPB/wt-89 cells at t…
Satb2 Regulates Callosal Projection Neuron Identity in the Developing Cerebral Cortex
2008
SummarySatb2 is a DNA-binding protein that regulates chromatin organization and gene expression. In the developing brain, Satb2 is expressed in cortical neurons that extend axons across the corpus callosum. To assess the role of Satb2 in neurons, we analyzed mice in which the Satb2 locus was disrupted by insertion of a LacZ gene. In mutant mice, β-galactosidase-labeled axons are absent from the corpus callosum and instead descend along the corticospinal tract. Satb2 mutant neurons acquire expression of Ctip2, a transcription factor that is necessary and sufficient for the extension of subcortical projections by cortical neurons. Conversely, ectopic expression of Satb2 in neural stem cells m…
RIP-Chip analysis supports different roles for AGO2 and GW182 proteins in recruiting and processing microRNA targets.
2019
Background MicroRNAs (miRNAs) are small non-coding RNA molecules mediating the translational repression and degradation of target mRNAs in the cell. Mature miRNAs are used as a template by the RNA-induced silencing complex (RISC) to recognize the complementary mRNAs to be regulated. To discern further RISC functions, we analyzed the activities of two RISC proteins, AGO2 and GW182, in the MCF-7 human breast cancer cell line. Methods We performed three RIP-Chip experiments using either anti-AGO2 or anti-GW182 antibodies and compiled a data set made up of the miRNA and mRNA expression profiles of three samples for each experiment. Specifically, we analyzed the input sample, the immunoprecipita…
ORGANIZATION OF HIGHER-LEVEL CHROMATIN STRUCTURES (CHROMOMERE, CHROMONEMA AND CHROMATIN BLOCK) EXAMINED USING VISIBLE LIGHT-INDUCED CHROMATIN PHOTO-S…
2002
The method of chromatin photo-stabilization by the action of visible light in the presence of ethidium bromide was used for investigation of higher-level chromatin structures in isolated nuclei. As a model we used rat hepatocyte nuclei isolated in buffers which stabilized or destabilized nuclear matrix. Several higher-level chromatin structures were visualized: 100 nm globules—chromomeres, chains of chromomeres—chromonemata, aggregates of chromomeres—blocks of condensed chromatin. All these structures were completely destroyed by 2 M NaCl extraction independent of the matrix state, and DNA was extruded from the residual nuclei (nuclear matrices) into a halo. These results show that nuclear …
MicroRNA-Based Therapeutic Perspectives in Myotonic Dystrophy
2019
Myotonic dystrophy involves two types of chronically debilitating rare neuromuscular diseases: type 1 (DM1) and type 2 (DM2). Both share similarities in molecular cause, clinical signs, and symptoms with DM2 patients usually displaying milder phenotypes. It is well documented that key clinical symptoms in DM are associated with a strong mis-regulation of RNA metabolism observed in patient’s cells. This mis-regulation is triggered by two leading DM-linked events: the sequestration of Muscleblind-like proteins (MBNL) and the mis-regulation of the CUGBP RNA-Binding Protein Elav-Like Family Member 1 (CELF1) that cause significant alterations to their important functions in RNA processing. It ha…
The structural plasticity of the C terminus of p21Cip1 is a determinant for target protein recognition.
2003
The cyclin-dependent kinase inhibitory protein p21(Cip1) might play multiple roles in cell-cycle regulation through interaction of its C-terminal domain with a defined set of cellular proteins such as proliferating cell nuclear antigen (PCNA), calmodulin (CaM), and the oncoprotein SET. p21(Cip1) could be described as an intrinsically unstructured protein in solution although the C-terminal domain adopts a well-defined extended conformation when bound to PCNA. However, the molecular mechanism of the interaction with CaM and the oncoprotein SET is not well understood, partly because of the lack of structural information. In this work, a peptide derived from the C-terminal domain of p21(Cip1) …
Benzo[a]pyrene represses DNA repair through altered E2F1/E2F4 function marking an early event in DNA damage-induced cellular senescence
2020
AbstractTranscriptional regulation of DNA repair is of outmost importance for the restoration of DNA integrity upon genotoxic stress. Here we report that the potent environmental carcinogen benzo[a]pyrene (B[a]P) activates a cellular DNA damage response resulting in transcriptional repression of mismatch repair (MMR) genes (MSH2, MSH6, EXO1) and of RAD51, the central homologous recombination repair (HR) component, ultimately leading to downregulation of MMR and HR. B[a]P-induced gene repression is caused by abrogated E2F1 signalling. This occurs through proteasomal degradation of E2F1 in G2-arrested cells and downregulation of E2F1 mRNA expression in G1-arrested cells. Repression of E2F1-me…
Presentation of an Immunodominant Immediate-Early CD8+ T Cell Epitope Resists Human Cytomegalovirus Immunoevasion.
2013
Control of human cytomegalovirus (HCMV) depends on CD8+ T cell responses that are shaped by an individual's repertoire of MHC molecules. MHC class I presentation is modulated by a set of HCMV-encoded proteins. Here we show that HCMV immunoevasins differentially impair T cell recognition of epitopes from the same viral antigen, immediate-early 1 (IE-1), that are presented by different MHC class I allotypes. In the presence of immunoevasins, HLA-A- and HLA-B-restricted T cell clones were ineffective, but HLA-C*0702-restricted T cell clones recognized and killed infected cells. Resistance of HLA-C*0702 to viral immunoevasins US2 and US11 was mediated by the alpha3 domain and C-terminal region …