Nucleolin is a histone chaperone with FACT-like activity and assists remodeling of nucleosomes (original) (raw)
Related papers
Journal of Biological Chemistry, 2000
SWI-SNF is an ATP-dependent chromatin remodeling complex required for expression of a number of yeast genes. Previous studies have suggested that SWI-SNF action may remove or rearrange the histone H2A-H2B dimers or induce a novel alteration in the histone octamer. Here, we have directly tested these and other models by quantifying the remodeling activity of SWI-SNF on arrays of (H3-H4) 2 tetramers, on nucleosomal arrays reconstituted with disulfide-linked histone H3, and on arrays reconstituted with histone H3 derivatives sitespecifically modified at residue 110 with the fluorescent probe acetylethylenediamine-(1,5)-naphthol sulfonate. We find that SWI-SNF can remodel (H3-H4) 2 tetramers, although tetramers are poor substrates for SWI-SNF remodeling compared with nucleosomal arrays. SWI-SNF can also remodel nucleosomal arrays that harbor disulfide-linked (H3-H4) 2 tetramers, indicating that SWI-SNF action does not involve an obligatory disruption of the tetramer. Finally, we find that although the fluorescence emission intensity of acetylethylenediamine-(1,5)naphthol sulfonate-modified histone H3 is sensitive to octamer structure, SWI-SNF action does not alter fluorescence emission intensity. These data suggest that perturbation of the histone octamer is not a requirement or a consequence of ATP-dependent nucleosome remodeling by SWI-SNF.
Genetics, 2013
The pob3-Q308K mutation alters the small subunit of the Saccharomyces cerevisiae histone/nucleosome chaperone Facilitates Chromatin Transactions (FACT), causing defects in both transcription and DNA replication. We describe histone mutations that suppress some of these defects, providing new insight into the mechanism of FACT activity in vivo. FACT is primarily known for its ability to promote reorganization of nucleosomes into a more open form, but neither the pob3-Q308K mutation nor the compensating histone mutations affect this activity. Instead, purified mutant FACT complexes fail to release from nucleosomes efficiently, and the histone mutations correct this flaw. We confirm that pob3-T252E also suppresses pob3-Q308K and show that combining two suppressor mutations can be detrimental, further demonstrating the importance of balance between association and dissociation for efficient FACT:nucleosome interactions. To explain our results, we propose that histone H4 can adopt multip...
A major nucleolar protein, nucleolin, induces chromatin decondensation by binding to histone Hl
European Journal of Biochemistry, 1988
Using circular dichroism to probe the extent of DNA condensation in chromatin, we have demonstrated that a major nucleolar protein, nucleolin, can decondense chromatin. By means of various binding assays we show that nucleolin has a strong affinity for histone H1 and that the phosphorylated N-terminal domain, rich in lengthy stretches of acidic amino acids, is responsible for this ionic interaction. Additional experiments clearly demonstrate that nucleolin is unable to act as a nucleosome core assembly or disassembly factor and hence has little affinity for the core histone octamer.
The FACT histone chaperone guides histone H 4 into its nucleosomal conformation in S . cerevisiae
2013
The pob3-Q308K mutation alters the small subunit of the Saccharomyces cerevisiae histone/nucleosome chaperone FACT, causing defects in both transcription and DNA replication. We describe histone mutations that suppress some of these defects, providing new insight into the mechanism of FACT activity in vivo. FACT is primarily known for its ability to promote reorganization of nucleosomes into a more open form, but neither the pob3-Q308K mutation nor the compensating histone mutations affect this activity. Instead, purified mutant FACT complexes fail to release from nucleosomes efficiently, and the histone mutations correct this flaw. We confirm that pob3-T252E also suppresses pob3-Q308K, and show that combining two suppressor mutations can be detrimental, further demonstrating the importance of balance between association and dissociation for efficient FACT:nucleosome interactions. To explain our results, we propose that histone H4 can adopt multiple conformations, most of which are ...
Nucleolin modulates compartmentalization and dynamics of histone 2B-ECFP in the nucleolus
Nucleus
Eukaryotic cells have 2 to 3 discrete nucleoli required for ribosome synthesis. Nucleoli are phase separated nuclear sub-organelles. Here we examined the role of nuclear Lamins and nucleolar factors in modulating the compartmentalization and dynamics of histone 2B (H2B-ECFP) in the nucleolus. Live imaging and Fluorescence Recovery After Photobleaching (FRAP) of labelled H2B, showed that the depletion of Lamin B1, Fibrillarin (FBL) or Nucleostemin (GNL3), enhances H2B-ECFP mobility in the nucleolus. Furthermore, Nucleolin knockdown significantly decreases H2B-ECFP compartmentalization in the nucleolus, while H2B-ECFP residence and mobility in the nucleolus was prolonged upon Nucleolin overexpression. Co-expression of N-terminal and RNA binding domain (RBD) deletion mutants of Nucleolin or inhibiting 45S rRNA synthesis reduces the sequestration of H2B-ECFP in the nucleolus. Taken together, these studies reveal a crucial role of Nucleolin-rRNA complex in modulating the compartmentalization, stability and dynamics of H2B within the nucleolus.
FACT Facilitates Transcription-Dependent Nucleosome Alteration
Science, 2003
The FACT (facilitates chromatin transcription) complex is required for transcript elongation through nucleosomes by RNA polymerase II (Pol II) in vitro. Here, we show that FACT facilitates Pol II–driven transcription by destabilizing nucleosomal structure so that one histone H2A-H2B dimer is removed during enzyme passage. We also demonstrate that FACT possesses intrinsic histone chaperone activity and can deposit core histones onto DNA. Importantly, FACT activity requires both of its constituent subunits and is dependent on the highly acidic C terminus of its larger subunit, Spt16. These findings define the mechanism by which Pol II can transcribe through chromatin without disrupting its epigenetic status.
Histone H2A/H2B Dimer Exchange by ATP-Dependent Chromatin Remodeling Activities
Molecular Cell, 2003
Histone chaperones physically interact with histones to direct proper assembly and disassembly of nucleosomes regulating diverse nuclear processes such as DNA replication, promoter remodelling, transcription elongation, DNA damage, and histone variant exchange. Currently, the best characterised chaperone-histone interaction is that between the ubiquitous chaperone Asf1 and a dimer of H3 and H4. Nucleosome Assembly Proteins (Nap proteins) represent a distinct class of histone chaperone. Using pulsed electron double resonance (PELDOR) measurements and protein cross-linking we show that two members of this class, Nap1 and Vps75, bind histones in the tetrameric conformation also observed when they are sequestered within the nucleosome. Furthermore, H3 and H4 trapped in their tetrameric state can be used as substrates in nucleosome assembly and chaperone mediated lysine acetylation. This alternate mode of histone interaction also provides a potential means of maintaining the integrity of the histone tetramer during cycles of nucleosome reassembly.
A Quantitative Characterization of Nucleoplasmin/Histone Complexes Reveals Chaperone Versatility
Scientific Reports, 2016
Nucleoplasmin (NP) is an abundant histone chaperone in vertebrate oocytes and embryos involved in storing and releasing maternal histones to establish and maintain the zygotic epigenome. NP has been considered a H2A-H2B histone chaperone, and recently it has been shown that it can also interact with H3-H4. However, its interaction with different types of histones has not been quantitatively studied so far. We show here that NP binds H2A-H2B, H3-H4 and linker histones with K d values in the subnanomolar range, forming different complexes. Post-translational modifications of NP regulate exposure of the polyGlu tract at the disordered distal face of the protein and induce an increase in chaperone affinity for all histones. The relative affinity of NP for H2A-H2B and linker histones and the fact that they interact with the distal face of the chaperone could explain their competition for chaperone binding, a relevant process in NP-mediated sperm chromatin remodelling during fertilization. Our data show that NP binds H3-H4 tetramers in a nucleosomal conformation and dimers, transferring them to DNA to form disomes and tetrasomes. This finding might be relevant to elucidate the role of NP in chromatin disassembly and assembly during replication and transcription. Xenopus laevis early embryogenesis is a process characterized by rapid cell division and transcriptional quiescence that depends on parental stored proteins, including histones 1. Histone chaperones bind these basic ligands to store or escort them to their final destinations 2 , and to modulate the post-translational modifications that regulate their chromatin remodelling activity 3-6. Nucleoplasmin (NPM2, here called NP), a member of the nucleophosmin/nucleoplasmin family of histone chaperones 7 , is involved in H2A-H2B storage and chromatin remodelling 8. NP forms stable homopentamers comprised of 22 kDa subunits that fold into a two domain structure (Fig. 1A): an eight-stranded β-barrel N-terminal core domain (residues 16-120) with a jelly roll topology (Fig. 1B) 7,9-12 , and the C-terminus tail that adopts a disordered conformation 13. NP contains three acidic tracts, A1, A2 (or polyGlu) and A3, the last two being part of the C-terminal intrinsically disordered domain (Fig. 1A) that builds the so-called distal face of the protein pentamer (Fig. 1C). This domain also contains the positively charged, bipartite nuclear localization sequence (NLS) (Fig. 1A) 7,14,15. Post-translational modifications (PTMs), in particular phosphorylation, of NP activates its chromatin decondensation activity, enhancing its ability to remove linker histones from DNA 16,17 , and increases its affinity for H2A-H2B and H5 18,19. NP co-immunoprecipitates not only with H2A-H2B but also with H3-H4 in Xenopus oocyte and egg extracts, suggesting that it can interact with both histones 20. Electron microscopy (EM) analysis of full-length, native NP from Xenopus laevis eggs (eNP), isolated and in complexes with H2A-H2B, H3-H4 or histone octamers shows the highly acidic distal face of the chaperone contacting all types of histones 19,20. Interestingly, the interaction of eNP with H2A-H2B, H3-H4 or the histone octamer results in different complexes. As seen by EM and analytical ultracentrifugation, one eNP pentamer can bind 5 H2A-H2B dimers at the distal face, whereas a larger ellipsoidal complex is formed with the H3-H4 tetramer either alone or as part of the histone octamer, in which the basic ligands are wrapped by the distal faces of two NP pentamers 20 .
Chromatin remodeling and transcription
Current Opinion in Genetics & Development, 1997
Recent advances highlight two important chromatin remodeling systems involved in the transcriptional process. One system includes several members of the evolutionarily conserved SWI2/SNF2 family found in distinct multiprotein complexes with ATP-dependent nucleosome destabilizing activity; the other is the enzymatic system that governs histone acetylation and deacetylation. Identification of the catalytic subunits of these opposing histone-modifying activities reveal conserved proteins defined genetically as transcriptional regulators.