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The Actin-Family Protein Arp4 Is a Novel Suppressor for the Formation and Functions of Nuclear F-Actin. Cells 2020; 9:cells9030758. [PMID: 32204557 PMCID: PMC7140684 DOI: 10.3390/cells9030758] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 03/06/2020] [Accepted: 03/17/2020] [Indexed: 12/20/2022] Open
Abstract
The crosstalk between actin and actin-related proteins (Arps), namely Arp2 and Arp3, plays a central role in facilitating actin polymerization in the cytoplasm and also in the nucleus. Nuclear F-actin is required for transcriptional regulation, double-strand break repair, and nuclear organization. The formation of nuclear F-actin is highly dynamic, suggesting the involvement of positive and negative regulators for nuclear actin polymerization. While actin assembly factors for nuclear F-actin have been recently described, information about inhibitory factors is still limited. The actin-related protein Arp4 which is predominantly localized in the nucleus, has been previously identified as an integral subunit of multiple chromatin modulation complexes, where it forms a heterodimer with monomeric actin. Therefore, we tested whether Arp4 functions as a suppressor of nuclear F-actin formation. The knockdown of Arp4 (Arp4 KD) led to an increase in nuclear F-actin formation in NIH3T3 cells, and purified Arp4 potently inhibited F-actin formation in mouse nuclei transplanted into Xenopus laevis oocytes. Consistently, Arp4 KD facilitated F-actin-inducible gene expression (e.g., OCT4) and DNA damage repair. Our results suggest that Arp4 has a critical role in the formation and functions of nuclear F-actin.
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Actin-related proteins regulate the RSC chromatin remodeler by weakening intramolecular interactions of the Sth1 ATPase. Commun Biol 2018; 1:1. [PMID: 29809203 PMCID: PMC5969521 DOI: 10.1038/s42003-017-0002-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The catalytic subunits of SWI/SNF-family and INO80-family chromatin remodelers bind actin and actin-related proteins (Arps) through an N-terminal helicase/SANT-associated (HSA) domain. Between the HSA and ATPase domains lies a conserved post-HSA (pHSA) domain. The HSA domain of Sth1, the catalytic subunit of the yeast SWI/SNF-family remodeler RSC, recruits the Rtt102-Arp7/9 heterotrimer. Rtt102-Arp7/9 regulates RSC function, but the mechanism is unclear. We show that the pHSA domain interacts directly with another conserved region of the catalytic subunit, protrusion-1. Rtt102-Arp7/9 binding to the HSA domain weakens this interaction and promotes the formation of stable, monodisperse complexes with DNA and nucleosomes. A crystal structure of Rtt102-Arp7/9 shows that ATP binds to Arp7 but not Arp9. However, Arp7 does not hydrolyze ATP. Together, the results suggest that Rtt102 and ATP stabilize a conformation of Arp7/9 that potentiates binding to the HSA domain, which releases intramolecular interactions within Sth1 and controls DNA and nucleosome binding. Bengi Turegun et al. report an interaction of the highly-conserved pHSA and P1 domains of Sth1, the catalytic subunit of the SWI/SNF-family chromatin remodeler RSC. This interaction is released when ATP-bound Rtt102-Arp7/9 binds to the HSA domain, modulating DNA and nucleosome binding by Sth.
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Actin, actin-related proteins and profilin in diatoms: A comparative genomic analysis. Mar Genomics 2015; 23:133-42. [DOI: 10.1016/j.margen.2015.07.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 06/30/2015] [Accepted: 07/02/2015] [Indexed: 12/24/2022]
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Osakabe A, Takahashi Y, Murakami H, Otawa K, Tachiwana H, Oma Y, Nishijima H, Shibahara KI, Kurumizaka H, Harata M. DNA binding properties of the actin-related protein Arp8 and its role in DNA repair. PLoS One 2014; 9:e108354. [PMID: 25299602 PMCID: PMC4191963 DOI: 10.1371/journal.pone.0108354] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 08/26/2014] [Indexed: 12/05/2022] Open
Abstract
Actin and actin-related proteins (Arps), which are members of the actin family, are essential components of many of these remodeling complexes. Actin, Arp4, Arp5, and Arp8 are found to be evolutionarily conserved components of the INO80 chromatin remodeling complex, which is involved in transcriptional regulation, DNA replication, and DNA repair. A recent report showed that Arp8 forms a module in the INO80 complex and this module can directly capture a nucleosome. In the present study, we showed that recombinant human Arp8 binds to DNAs, and preferentially binds to single-stranded DNA. Analysis of the binding of adenine nucleotides to Arp8 mutants suggested that the ATP-binding pocket, located in the evolutionarily conserved actin fold, plays a regulatory role in the binding of Arp8 to DNA. To determine the cellular function of Arp8, we derived tetracycline-inducible Arp8 knockout cells from a cultured human cell line. Analysis of results obtained after treating these cells with aphidicolin and camptothecin revealed that Arp8 is involved in DNA repair. Together with the previous observation that Arp8, but not γ-H2AX, is indispensable for recruiting INO80 complex to DSB in human, results of our study suggest an individual role for Arp8 in DNA repair.
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Affiliation(s)
- Akihisa Osakabe
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
| | - Yuichiro Takahashi
- Laboratory of Molecular Biology, Graduate School of Agricultural Science, Tohoku University, Sendai, Japan
| | - Hirokazu Murakami
- Laboratory of Molecular Biology, Graduate School of Agricultural Science, Tohoku University, Sendai, Japan
| | - Kenji Otawa
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
| | - Hiroaki Tachiwana
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
| | - Yukako Oma
- Laboratory of Molecular Biology, Graduate School of Agricultural Science, Tohoku University, Sendai, Japan
| | - Hitoshi Nishijima
- Department of Integrated Genetics, National Institute of Genetics, Mishima, Japan
| | - Kei-ich Shibahara
- Department of Integrated Genetics, National Institute of Genetics, Mishima, Japan
| | - Hitoshi Kurumizaka
- Laboratory of Structural Biology, Graduate School of Advanced Science and Engineering, Waseda University, Tokyo, Japan
- * E-mail: (HK); (MH)
| | - Masahiko Harata
- Laboratory of Molecular Biology, Graduate School of Agricultural Science, Tohoku University, Sendai, Japan
- * E-mail: (HK); (MH)
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Turegun B, Kast DJ, Dominguez R. Subunit Rtt102 controls the conformation of the Arp7/9 heterodimer and its interactions with nucleotide and the catalytic subunit of SWI/SNF remodelers. J Biol Chem 2013; 288:35758-68. [PMID: 24189066 DOI: 10.1074/jbc.m113.514083] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chromatin-remodeling complexes are assembled around a catalytic subunit that contains a central ATPase domain and flanking sequences that recruit auxiliary subunits. The catalytic subunits of SWI/SNF remodelers recruit Arp7/9 through a helicase/SANT-associated (HSA) domain N-terminal to the ATPase domain. Arp7/9-containing remodelers also carry the auxiliary subunit Rtt102, but the role of this subunit is poorly understood. Here, we show that Rtt102 binds with nanomolar affinity to the Arp7/9 heterodimer and modulates its conformation and interactions with the ATPase subunit and nucleotide. When bound to Rtt102, Arp7/9 interacts with a shorter segment of the HSA domain. Structural analysis by small-angle x-ray scattering further shows that when bound to Rtt102, the complex of Arp7/9 with the catalytic subunit assumes a more stable compact conformation. We also found that Arp7, Arp9, and Arp7/9 interact very weakly with ATP, but Rtt102 promotes high-affinity ATP binding to a single site in the heterodimer. Collectively, the results establish a function for subunit Rtt102 as a stabilizing factor for the Arp7/9 heterodimer, enhancing its interaction with nucleotide and controlling the conformation of SWI/SNF remodelers in an Arp7/9-dependent manner.
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Miyamoto K, Gurdon JB. Transcriptional regulation and nuclear reprogramming: roles of nuclear actin and actin-binding proteins. Cell Mol Life Sci 2013; 70:3289-302. [PMID: 23275942 PMCID: PMC3753470 DOI: 10.1007/s00018-012-1235-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 12/03/2012] [Accepted: 12/04/2012] [Indexed: 12/18/2022]
Abstract
Proper regulation of transcription is essential for cells to acquire and maintain cell identity. Transcriptional activation plays a central role in gene regulation and can be modulated by introducing transcriptional activators such as transcription factors. Activators act on their specific target genes to induce transcription. Reprogramming experiments have revealed that as cells become differentiated, some genes are highly silenced and even introduction of activators that target these silenced genes does not induce transcription. This can be explained by chromatin-based repression that restricts access of transcriptional activators to silenced genes. Transcriptional activation from these genes can be accomplished by opening chromatin, in addition to providing activators. Once a de novo transcription network is established, cells are differentiated or reprogrammed to a new cell type. Emerging evidence suggests that actin in the nucleus (nuclear actin) and nuclear actin-binding proteins are implicated in these transcriptional regulatory processes. This review summarizes roles of nuclear actin and actin-binding proteins in transcriptional regulation. We also discuss possible functions of nuclear actin during reprogramming in the context of transcription and chromatin remodeling.
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Affiliation(s)
- Kei Miyamoto
- The Wellcome Trust/Cancer Research UK Gurdon Institute, The Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QN, UK.
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Fenn S, Gerhold CB, Hopfner KP. Nuclear actin-related proteins take shape. BIOARCHITECTURE 2011; 1:192-195. [PMID: 22069513 DOI: 10.4161/bioa.1.4.17643] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 08/04/2011] [Indexed: 12/30/2022]
Abstract
The function of nuclear actin is poorly understood. It is known to be a discrete component of several chromatin-modifying complexes. Nevertheless, filamentous forms of actin are important for various nuclear processes as well. Nuclear actin is often associated with nuclear actin-related protein Arp4 and other actin-related proteins like Arp8 in the INO80 chromatin remodeler. We recently determined the crystal structure of S. cerevisiae Arp4 that explains why Arp4 is unable to form actin like filaments and shows that it is constitutively bound to an ATP nucleotide. More interestingly, in vitro activities of Arp4 and Arp8 seem to be directed towards stabilizing monomeric actin and to integrate it stoichiometrically into the INO80 complex. Based on this activity, we discuss possible roles of nuclear Arps in chromatin modifying complexes and in regulating more general aspects of nuclear actin dynamics.
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