Chromatin

Phát triển là quá trình kiểm soát sự biểu hiện gen, quá trình điều hòa phức tạp về cơ chế, cơ bản có 5 mức độ: 1- Sự xoắn của NST (Chromatin Packing) 2- Kiểm soát sự phiên mã (Transcriptional Control) 3- Điều hòa hậu phiên mã (Posttranscriptional) [Nhân tế bào (Nuclear levels)] 4- Kiểm soát sự giải mã (Translational Control) 5- Điều hòa hậu giải mã (Posttranslational Control) [Cytosol (Cytoplasmic levels)] Sự điều hòa phiên mã bởi những phân tử protein,yếu tố phiên mã (transcription factors -TF). Các phân tử protein này luôn hiện diện trong tế bào và bám...

62p bichtram1910 22-05-2012 250 38   Download

Basic Cell Biology I. Cytoplasm A. Plasma membrane B. Mitochondria C. Ribosomes D. Endoplasmic reticulum 1. Rough 2. Smooth E. Golgi apparatus F. Lysosomes G. Cytoskeleton II. Nucleus A. Nuclear Envelope B. Chromatin C. Nucleolus D. Nuclear matrix III. Cell division .© 2002 by Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter. .Asymmetrical arrangement of phospholipids in plasma membrane ATP-dependent phospholipid translocase .Molecular Cell Biology, Lodish et al., 4th edition. .Figure 2—1.

68p whitedaisy1010 26-02-2013 63 12   Download

Bài giảng Những điểm mới trong điều trị viêm gan B mạn hiện nay trình bày các nội dung chính sau: Lược qua về thực hành điều trị hiện nay, những hiểu biết quan trọng về nhiễm HBV,... Mời các bạn cùng tham khảo để nắm nội dung chi tiết của bài giảng.

36p viguam2711 06-01-2021 35 2   Download

DNA transactions in eukaryotes require that proteins gain access to target sequences packaged in chromatin. Further, interactions between distinct nucleoprotein complexes are often required to generate higher-order structures. Here, we employed two prokaryotic site-specific recombination systems to investigate how chromatin packaging affects the assembly of nucleoprotein structures of different complexities at more than 30 genomic loci. The dynamic nature of chromatin permitted protein–DNA and DNA–DNA interactions for sites of at least 34 bp in length.

7p system191 01-06-2013 55 4   Download

Hypoxia interrupts the initiation of simian virus 40 (SV40) replication in vivo at a stage situated before unwinding of the origin region. After re-oxygenation, unwinding followed by a synchronous round of viral replication takes place. To further characterize the hypoxia-induced inhibition of unwinding, we analysed the binding of several replication proteins to the viral minichromosome before and after re-oxygenation.

11p research12 01-06-2013 41 4   Download

Chromatin is a highly dynamic structure that plays an essential role in regulating all nuclear processes that utilize the DNA template including DNA repair, replication, transcription and recombination. Thus, the mechanisms by which chromatin structures are assembled and modified are questions of broad interest. This minireview will focus on two groups of proteins: (a) histone chaperones and (b) ATPdependent chromatin remodeling machines, that co-operate to assemble DNA and histone proteins into chromatin....

7p research12 01-06-2013 36 4   Download

Nuclear receptors (NRs) are ligand-regulated, DNA-binding transcription factors that function in the chromatin environment of the nucleus to alter the expression of subsets of hormone-responsive genes. It is clear that chromatin, rather than being a passive player, has a profound effect on both transcriptional repression and activation mediated by NRs.

9p research12 01-06-2013 32 2   Download

Nuclear cloning is a procedure to create new animals by injecting somatic nuclei into unfertilized oocytes. Recent successes in mammalian cloning with differentiated adult nuclei strongly indicate that oocyte cytoplasm contains unidentified remarkable reprogramming activities with the capacity to erase the previous memory of cell differentiation. At the heart of this nuclear reprogramming lies chromatin remodeling as chromatin structure and function define cell differentiation through regulation of the transcriptional activities of the cells....

4p research12 01-06-2013 43 4   Download

The organization of DNA within eukaryotic cell nuclei poses special problems and opportunities for the cell. For example, assembly of DNA into chromatin is thought to be a principle mechanism by which adventitious general transcription is repressed. However, access to genomic DNA for events such as DNA repair must be facilitated by energy-intensive processes that either directly alter chromatin structure or impart post-translational modifications, leading to increased DNA accessibility.

6p research12 01-06-2013 36 4   Download

The centromere–kinetochore complex is a highly specialized chromatin domain that both mediates and monitors chromosome–spindle interactions responsible for accurate partitioning of sister chromatids to daughter cells. Centromeres are distinguished from adjacent chromatin by specific patterns of histone modification and the presence of a centromere-specific histone H3 variant (e.g. CENP-A). Centromere-proximal regions usually correspond to sites of avid and persistent sister chromatid cohesion mediated by the conserved cohesin complex.

15p research12 01-06-2013 50 4   Download

During the development of multicellular organisms, both transient and stable gene expression patterns have to be established in a precisely orchestrated sequence. Evidence from diverse model organisms indicates that this epigenetic program involves not only transcription factors, but also the local structure, composition, and modification of chromatin, which define and maintain the accessibility and transcriptional competence of the nucleosomal DNA template.

6p research12 01-06-2013 33 4   Download

To search for novel regulatory regions, we examined the features of chromatin structure in the rat B29/Ig-b gene and its flanking regions by determining DNase I hypersensitive sites (DHS) in plasmacytoma-derived Y3 cells. Six Y3 cellspecific DHS were detected at )8.6, promoter, +0.7, +4.4, +6.0, and +8.7 kb. The DHS at +4.4, +6.0, and +8.7 kb were present in the intergenic region between B29/Ig-b and growth hormone (GH) genes and were mapped inside conserved sequences in rat and humans.

10p research12 01-06-2013 30 4   Download

The human replication protein Cdc6p is translocated from its chromatin sites to the cytoplasm during the replication phase (S phase) of the cell cycle. However, the amounts of Cdc6p on chromatin remain high during S phase implying either that displaced Cdc6p can rebind to chromatin, or that Cdc6p is synthesized de novo. We have performed metabolic labeling experiments and determined that [35S]methionine is incorporated into Cdc6p at similar rates during the G1 phase and the S phase of the cell cycle. Newly synthesized Cdc6p associates with chromatin....

7p research12 01-06-2013 41 3   Download

Binding of lamin B receptor (LBR) to chromatin was studied by means of an in vitro assay system involving recombinant fragments of human LBR and Xenopus sperm chromatin. Glutathione-S-transferase (GST)-fused proteins including LBR fragments containing the N-terminal region (residues 1–53) and arginine-serine repeat-containing region (residues 54–89) bound to chromatin. The binding of GST-fusion proteins incorporating the N-terminal and arginine-serine repeat-containing regions to chromatin was suppressed by mild trypsinization of the chromatin and by pretreatment with a DNA solution....

11p research12 01-06-2013 30 4   Download

Pisum sativump16 is a protein present in the chromatin of ungerminated embryonic axes. The purification of p16 and the isolationof a cDNAclone ofpsp54, the gene encoding its precursor have been recently reported [Castillo, J., Rodrigo, M. I.,Ma´rquez, J. A., Zu´n˜iga, AandFranco, L. (2000)Eur. J.Biochem.267, 2156–2165]. In thepresentpaper,wepresent data showing that p16 is a nuclear protein.

8p research12 23-04-2013 38 2   Download

Protamine-like proteins constitute a group of sperm nuclear basic proteins that have been shown to be related to somatic linker histones (histone H1 family). Like protamines, they usually replace the chromatin somatic his-tone complement during spermiogenesis; hence their name. Several of these proteins have been characterized to date in invertebrate organisms, but information about their occurrence and characterization in vertebrates is still lacking.

14p tumor12 20-04-2013 42 3   Download

It was shown previously [Riedinger, H. J., van Betteraey-Nikoleit, M & Probst, H. (2002)Eur. J. Biochem.269, 2383–2393] that initiation ofin vivo SV40 DNA replication is reversibly suppressed by hypoxia in a state where viral minichromosomes exhibit a nearly complete set of repli-cation proteins. Reoxygenation triggers fast completion and post-translational modifications.

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A histone heterodimer, designated as p28, which contains an N e (c-glutamyl)lysine cross-link between Gln9 of histone H2B and Lys5 or Lys12 of histone H4, is present in starfish (Asterina pectinifera) sperm. Treatment of spermnuclei with micrococcal nuclease produced soluble chromatin, which was size-fractionated by sucrose-gradient centrifugation to give p28-containing oligonucleosome and p28-free mono-nucleosome fractions, indicating that the cross-link is inter-nucleosomal.

10p tumor12 20-04-2013 42 4   Download

Methyl-CpG-binding protein 2 (MeCP2) is a multifunc-tional protein involved in chromatin organization and silencing of methylated DNA. MAR-BD, a 125-amino-acid residue domain of chicken MeCP2 (cMeCP2, origin-ally named ARBP), is the minimal protein fragment required to recognize MAR elements and mouse satellite DNA. Here we report the solution structure of MAR-BD as determined by multidimensional heteronuclear NMR spectroscopy.

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Recent research suggests that minor changes in the primary sequence of the conserved histones may become major determinants for the chromatin structure regulating gene expression and other DNA-related processes. An analysis of the involvement of different core histone variants in different nuclear processes and the structure of different variant nucleosome cores shows that this may indeed be so. Histone variants may also be involved in demarcating functional regions of the chromatin.

20p fptmusic 12-04-2013 38 4   Download