The Requirement of H1 Histones for a Heterodimeric Nuclear Import Receptor

Bäuerle, Marc; Doenecke, Detlef; Albig, Werner

doi:10.1074/jbc.m202765200

Cited by 44 publications

(60 citation statements)

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“…Previous studies revealed the Imp␤⅐Imp7 heterodimer to be the only functional import receptor for H1 linker histones (12,13). The binding sites on Imp␤ for Imp7 and H1 0 have already been identified (12) and include HEAT repeats 4 -9 (Imp7) and HEAT repeats 6 -19 (H1 0 ).…”

Section: Resultsmentioning

confidence: 99%

“…In Vitro Nuclear Import Assays and Immunofluorescence Detection-Preparation of the fluorescent import substrates 4z-rpL23a and 6z-H1 0 was done as described (10,13). The permeabilization of HeLa cells, the preparation of the energy regenerating system, and the Ran mix were done according to the protocol of Adam et al (18) and modifications described by Jäkel and Görlich (10).…”

Section: Recombinant Protein Expression and Protein Purification-mentioning

confidence: 99%

“…Expression and purification was analogous to that of the Imp␤ fragments. H1 0 was expressed and purified as described previously (13). Recombinant H1.2 from B. taurus was purchased from Axxora, Germany.…”

Section: Recombinant Protein Expression and Protein Purification-mentioning

confidence: 99%

“…The functional import receptor for H1 is the Imp␤⅐Imp7 heterodimer (12,13). Only upon dimerization of Imp␤ and Imp7, a cooperative binding to H1 occurs (13). The ternary Imp␤⅐Imp7⅐H1 complex then translocates through the nuclear pore and after translocation sticks to the nuclear basket.…”

mentioning

confidence: 99%

“…A prominent example for such coimport pathways is the nuclear import of H1 linker histones. The functional import receptor for H1 is the Imp␤⅐Imp7 heterodimer (12,13). Only upon dimerization of Imp␤ and Imp7, a cooperative binding to H1 occurs (13).…”

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confidence: 99%

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Thermodynamic Analysis of H1 Nuclear Import

Wohlwend

Strasser

Dickmanns

et al. 2007

Journal of Biological Chemistry

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The nuclear import of H1 linker histones is mediated by a heterodimer of transport receptors, known as importin␤ and importin7. Interestingly, both importins separately interact with H1, but only as a dimer they facilitate the translocation through the nuclear pore. We identified the H1 binding site of importin7, comprising two extended acidic loops near the C terminus of importin7. The analysis of the H1 import complex assembly by means of isothermal titration calorimetry revealed that the formation of a receptor heterodimer in vitro is an enthalpy-driven process, whereas subsequent binding of H1 to the heterodimer is entropy-driven. Furthermore, we show that the importin␤ binding domain of importin7 plays a key role in the activation of importin7 by importin␤. This process is allosterically regulated by importin␤ and accounts for a specific tuning of the activity of the importin␤⅐importin7 heterodimer. The results presented here provide new insights into cellular strategies to even energy balances in nuclear import and point toward a general regulation of importin␤-related nuclear import processes.The nuclear transport machinery represents one of the major transport systems in eukaryotic cells connecting the nucleus and the cytosol by bridging the nuclear envelope. Nuclear pore complexes (NPCs) 2 are embedded in the nuclear envelope and provide the channels for nuclear transport. NPCs have a dual function; whereas solutes, ions and small macromolecules (20 -40 kDa) are allowed to diffuse passively through the nuclear pore, larger macromolecules or such, whose transfer has to be tightly controlled, are transported by specific, soluble transport receptors in a signal-dependent manner (for review, see Refs. 1-4). The majority of known transport signals are specifically recognized by members of the importin␤/karyopherin␤ protein superfamily shuttling between nucleus and cytosol, also known as importins and exportins. They are composed of a number of helix-turn-helix motifs termed HEAT tandem repeats, which pack side by side in an almost parallel fashion, forming elongated molecules with a superhelical twist (5-8). Besides one or more substrate binding sites, these proteins additionally comprise a binding site for the small GTPase Ran (9). Ran represents the central mediator of directionality of nucleocytoplasmic trafficking. Its low intrinsic GTPase activity allows for a rigid control of GTP hydrolysis. The cytosolic GTPase-activating protein RanGAP1 acts as activator of Ran; the additional factors RanBP1 and RanBP2 act as GTPase enhancers and further stimulate Ran's GTP hydrolysis rate. Due to the nucleocytoplasmic compartmentalization of the regulatory factors, with RanGAP in the cytosol and RanGEF in the nucleus, a steep gradient of RanGTP is established across the nuclear envelope with high concentrations in the nucleus and low ones in the cytosol. The RanGTP gradient across the nuclear envelope is thought to provoke a unidirectional translocation of cargoes through the NPC; in terms of nuclear import, bindi...

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Section: Resultsmentioning

confidence: 99%

Section: Recombinant Protein Expression and Protein Purification-mentioning

confidence: 99%

Section: Recombinant Protein Expression and Protein Purification-mentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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Thermodynamic Analysis of H1 Nuclear Import

Wohlwend

Strasser

Dickmanns

et al. 2007

Journal of Biological Chemistry

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Chemical Carcinogenesis and Epigenetics

Darwanto¹,

Ornam²,

Lao³

et al. 2010

Chemical Carcinogenesis

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Physical Mechanisms of Bacterial Killing by Histones

Doolin

Gross

Siryaporn

2020

Advances in Experimental Medicine and Biology

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Antibiotic resistance is a global epidemic, becoming increasingly pressing due to its rapid spread. There is thus a critical need to develop new therapeutic approaches. In addition to searching for new antibiotics, looking into existing mechanisms of natural host defense may enable researchers to improve existing defense mechanisms, and to develop effective, synthetic drugs guided by natural principles. Histones, primarily known for their role in condensing mammalian DNA, are antimicrobial and share biochemical similarities with antimicrobial peptides (AMPs); however, the mechanism by which histones kill bacteria is largely unknown. Both AMPs and histones are similar in size, cationic, contain a high proportion of hydrophobic amino acids, and possess the ability to form alpha helices. AMPs, which mostly kill bacteria through permeabilization or disruption of the biological membrane, have recently garnered significant attention for playing a key role in host defenses. This chapter outlines the structure and function of histone proteins as they compare to AMPs and provides an overview of their role in innate immune responses, especially regarding the action of specific histones against 1.1 Introduction In 1922, Alexander Fleming discovered lysozyme from nasal mucus 1. This was the first human antimicrobial protein to be reported; however, the discovery of penicillin in 1928 2 overshadowed this finding, and ushered the world into the "Golden Age" of antibiotics. Recently, the rise of antibiotic resistance, combined with the stagnation in discovering new, viable antimicrobial agents, has sparked renewed interest in natural host defenses. The antimicrobial activity of histones was first reported in 1942 3 and in vitro histone killing of bacteria was further characterized in 1958 using Escherichia coli 4. However, despite originally being proposed to function as antimicrobial agents, the role of histones in condensing eukaryotic DNA became seen as their primary function and little is known about their antimicrobial role and the possible mechanisms by which they kill bacteria. The discovery that histones have a central role in innate immune responses 5 has renewed interest into understanding their antimicrobial functions. Eukaryotic organisms possess a cell nucleus and other organelles enclosed within a membrane. Their nuclei contain genetic material, typically encoded in DNA, within a nuclear envelope. Within the nucleus, small, alkaline histone proteins are used to package the DNA into 5 nm nucleosomes that condense chromatin, the chromosomal material in eukaryotic cells that is composed protein, DNA, and a small amount of RNA. The basic structural unit of chromatin is made up of 146 DNA base pairs wrapped roughly 1.5 times around a histone core. This histone core structure is made up of eight histone components: two H2A-H2B dimers and a H3-H4 tetramer 6. These core histones are highly conserved through evolution, containing the 'helix turn helix turn helix' central motif, named the histone fold, and an unstructured a...

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The Requirement of H1 Histones for a Heterodimeric Nuclear Import Receptor

Cited by 44 publications

References 37 publications

Thermodynamic Analysis of H1 Nuclear Import

Thermodynamic Analysis of H1 Nuclear Import

Chemical Carcinogenesis and Epigenetics

Physical Mechanisms of Bacterial Killing by Histones

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