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  1. Article ; Online: Conservation of telomere protein complexes: shuffling through evolution.

    Linger, Benjamin R / Price, Carolyn M

    Critical reviews in biochemistry and molecular biology

    2009  Volume 44, Issue 6, Page(s) 434–446

    Abstract: The rapid evolution of telomere proteins has hindered identification of orthologs from diverse species and created the impression that certain groups of eukaryotes have largely non-overlapping sets of telomere proteins. However, the recent identification ...

    Abstract The rapid evolution of telomere proteins has hindered identification of orthologs from diverse species and created the impression that certain groups of eukaryotes have largely non-overlapping sets of telomere proteins. However, the recent identification of additional telomere proteins from various model organisms has dispelled this notion by expanding our understanding of the composition, architecture and range of telomere protein complexes present in individual species. It is now apparent that versions of the budding yeast CST complex and mammalian shelterin are present in multiple phyla. While the precise subunit composition and architecture of these complexes vary between species, the general function is often conserved. Despite the overall conservation of telomere protein complexes, there is still considerable species-specific variation, with some organisms having lost a particular subunit or even an entire complex. In some cases, complex components appear to have migrated between the telomere and the telomerase RNP. Finally, gene duplication has created telomere protein paralogs with novel functions. While one paralog may be part of a conserved telomere protein complex and have the expected function, the other paralog may serve in a completely different aspect of telomere biology.
    MeSH term(s) Animals ; Evolution, Molecular ; Genes, Duplicate ; Humans ; Protein Binding ; Telomere/genetics ; Telomere/metabolism ; Telomere-Binding Proteins/chemistry ; Telomere-Binding Proteins/genetics ; Telomere-Binding Proteins/metabolism
    Chemical Substances Telomere-Binding Proteins
    Language English
    Publishing date 2009-10-14
    Publishing country England
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Review
    ZDB-ID 1000977-2
    ISSN 1549-7798 ; 1381-3455 ; 1040-9238
    ISSN (online) 1549-7798
    ISSN 1381-3455 ; 1040-9238
    DOI 10.3109/10409230903307329
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: The Pot1a-associated proteins Tpt1 and Pat1 coordinate telomere protection and length regulation in Tetrahymena.

    Linger, Benjamin R / Morin, Gregg B / Price, Carolyn M

    Molecular biology of the cell

    2011  Volume 22, Issue 21, Page(s) 4161–4170

    Abstract: We have identified two new telomere proteins, Tpt1 and Pat1, from the ciliate Tetrahymena thermophila. Although Tetrahymena telomerase is well characterized, only one telomere protein had previously been identified. This was the G-overhang binding- ... ...

    Abstract We have identified two new telomere proteins, Tpt1 and Pat1, from the ciliate Tetrahymena thermophila. Although Tetrahymena telomerase is well characterized, only one telomere protein had previously been identified. This was the G-overhang binding-protein Pot1a. Tpt1 and Pat1 were isolated as Pot1a binding partners and shown to localize to telomeres. As Tpt1 and Pat1 were both found to be essential, conditional cell lines were generated to explore their function. Tpt1 depletion caused a rapid growth arrest and telomere elongation in the absence of cell division. The phenotype was similar to that seen after Pot1a depletion suggesting that Tpt1 and Pot1a function together to regulate telomere length and prevent telomere deprotection. In contrast, Pat1 depletion had a modest effect on cell growth but caused progressive telomere shortening similar to that observed upon TERT depletion. Thus Pat1 appears to be needed for telomerase to maintain the chromosome terminus. Analysis of Pot1a-Tpt1-Pat1 complex formation using purified proteins indicated that Tpt1 interacts directly with Pot1a while Pat1 interacts with Tpt1. Our results indicate that Tpt1 is the Tetrahymena equivalent of mammalian TPP1, Schizosaccharomyces pombe Tpz1, and Oxytricha nova TEBPβ.
    MeSH term(s) Chromatography, Affinity ; Cloning, Molecular ; Immunoprecipitation ; Multiprotein Complexes/metabolism ; Organisms, Genetically Modified ; Protein Binding ; Protozoan Proteins/genetics ; Protozoan Proteins/isolation & purification ; Protozoan Proteins/metabolism ; Recombinant Fusion Proteins/genetics ; Recombinant Fusion Proteins/isolation & purification ; Recombinant Fusion Proteins/metabolism ; Telomerase/metabolism ; Telomere/metabolism ; Telomere Homeostasis ; Tetrahymena thermophila/genetics ; Tetrahymena thermophila/growth & development ; Tetrahymena thermophila/metabolism
    Chemical Substances Multiprotein Complexes ; Protozoan Proteins ; Recombinant Fusion Proteins ; Telomerase (EC 2.7.7.49)
    Language English
    Publishing date 2011-09-07
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 1098979-1
    ISSN 1939-4586 ; 1059-1524
    ISSN (online) 1939-4586
    ISSN 1059-1524
    DOI 10.1091/mbc.E11-06-0551
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Tetrahymena Pot2 is a developmentally regulated paralog of Pot1 that localizes to chromosome breakage sites but not to telomeres.

    Cranert, Stacey / Heyse, Serena / Linger, Benjamin R / Lescasse, Rachel / Price, Carolyn

    Eukaryotic cell

    2014  Volume 13, Issue 12, Page(s) 1519–1529

    Abstract: Tetrahymena telomeres are protected by a protein complex composed of Pot1, Tpt1, Pat1, and Pat2. Pot1 binds the 3' overhang and serves multiple roles in telomere maintenance. Here we describe Pot2, a paralog of Pot1 which has evolved a novel function ... ...

    Abstract Tetrahymena telomeres are protected by a protein complex composed of Pot1, Tpt1, Pat1, and Pat2. Pot1 binds the 3' overhang and serves multiple roles in telomere maintenance. Here we describe Pot2, a paralog of Pot1 which has evolved a novel function during Tetrahymena sexual reproduction. Pot2 is unnecessary for telomere maintenance during vegetative growth, as the telomere structure is unaffected by POT2 macronuclear gene disruption. Pot2 is expressed only in mated cells, where it accumulates in developing macronuclei around the time of two chromosome processing events: internal eliminated sequence (IES) excision and chromosome breakage. Chromatin immunoprecipitation (ChIP) demonstrated Pot2 localization to regions of chromosome breakage but not to telomeres or IESs. Pot2 association with chromosome breakage sites (CBSs) occurs slightly before chromosome breakage. Pot2 did not bind CBSs or telomeric DNA in vitro, suggesting that it is recruited to CBSs by another factor. The telomere proteins Pot1, Pat1, and Tpt1 and the IES binding factor Pdd1 fail to colocalize with Pot2. Thus, Pot2 is the first protein found to associate specifically with CBSs. The selective association of Pot2 versus Pdd1 with CBSs or IESs indicates a mechanistic difference between the chromosome processing events at these two sites. Moreover, ChIP revealed that histone marks characteristic of IES processing, H3K9me3 and H3K27me3, are absent from CBSs. Thus, the mechanisms of chromosome breakage and IES excision must be fundamentally different. Our results lead to a model where Pot2 directs chromosome breakage by recruiting telomerase and/or the endonuclease responsible for DNA cleavage to CBSs.
    MeSH term(s) Chromosome Breakpoints ; DNA-Binding Proteins/metabolism ; Gene Expression ; Protein Binding ; Protein Transport ; Protozoan Proteins/metabolism ; Telomere/metabolism ; Telomere Homeostasis ; Tetrahymena thermophila/metabolism
    Chemical Substances DNA-Binding Proteins ; Protozoan Proteins
    Language English
    Publishing date 2014-10-10
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 2077635-4
    ISSN 1535-9786 ; 1535-9778
    ISSN (online) 1535-9786
    ISSN 1535-9778
    DOI 10.1128/EC.00204-14
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: The 3' overhangs at Tetrahymena thermophila telomeres are packaged by four proteins, Pot1a, Tpt1, Pat1, and Pat2.

    Premkumar, Vidjaya Letchoumy / Cranert, Stacey / Linger, Benjamin R / Morin, Gregg B / Minium, Sasha / Price, Carolyn

    Eukaryotic cell

    2013  Volume 13, Issue 2, Page(s) 240–245

    Abstract: Although studies with the ciliate Tetrahymena thermophila have played a central role in advancing our understanding of telomere biology and telomerase mechanisms and composition, the full complement of Tetrahymena telomere proteins has not yet been ... ...

    Abstract Although studies with the ciliate Tetrahymena thermophila have played a central role in advancing our understanding of telomere biology and telomerase mechanisms and composition, the full complement of Tetrahymena telomere proteins has not yet been identified. Previously, we demonstrated that in Tetrahymena, the telomeric 3' overhang is protected by a three-protein complex composed of Pot1a, Tpt1, and Pat1. Here we show that Tpt1 and Pat1 associate with a fourth protein, Pat2 (Pot1 associated Tetrahymena 2). Mass spectrometry of proteins copurifying with Pat1 or Tpt1 identified peptides from Pat2, Pot1a, Tpt1, and Pat1. The lack of other proteins copurifying with Pat1 or Tpt1 implies that the overhang is protected by a four-protein Pot1a-Tpt1-Pat1-Pat2 complex. We verified that Pat2 localizes to telomeres, but we were unable to detect direct binding to telomeric DNA. Cells depleted of Pat2 continue to divide, but the telomeres exhibit gradual shortening. The lack of growth arrest indicates that, in contrast to Pot1a and Tpt1, Pat2 is not required for the sequestration of the telomere from the DNA repair machinery. Instead, Pat2 is needed to regulate telomere length, most likely by acting in conjunction with Pat1 to allow telomerase access to the telomere.
    MeSH term(s) 3' Flanking Region ; DNA, Protozoan/metabolism ; Protein Binding ; Protozoan Proteins/genetics ; Protozoan Proteins/metabolism ; Telomere/genetics ; Telomere/metabolism ; Telomere-Binding Proteins/genetics ; Telomere-Binding Proteins/metabolism ; Tetrahymena thermophila/genetics ; Tetrahymena thermophila/metabolism
    Chemical Substances DNA, Protozoan ; Protozoan Proteins ; Telomere-Binding Proteins
    Language English
    Publishing date 2013-12-02
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 2077635-4
    ISSN 1535-9786 ; 1535-9778
    ISSN (online) 1535-9786
    ISSN 1535-9778
    DOI 10.1128/EC.00275-13
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Role of sindbis virus capsid protein region II in nucleocapsid core assembly and encapsidation of genomic RNA.

    Warrier, Ranjit / Linger, Benjamin R / Golden, Barbara L / Kuhn, Richard J

    Journal of virology

    2008  Volume 82, Issue 9, Page(s) 4461–4470

    Abstract: Sindbis virus is an enveloped positive-sense RNA virus in the alphavirus genus. The nucleocapsid core contains the genomic RNA surrounded by 240 copies of a single capsid protein. The capsid protein is multifunctional, and its roles include acting as a ... ...

    Abstract Sindbis virus is an enveloped positive-sense RNA virus in the alphavirus genus. The nucleocapsid core contains the genomic RNA surrounded by 240 copies of a single capsid protein. The capsid protein is multifunctional, and its roles include acting as a protease, controlling the specificity of RNA that is encapsidated into nucleocapsid cores, and interacting with viral glycoproteins to promote the budding of mature virus and the release of the genomic RNA into the newly infected cell. The region comprising amino acids 81 to 113 was previously implicated in two processes, the encapsidation of the viral genomic RNA and the stable accumulation of nucleocapsid cores in the cytoplasm of infected cells. In the present study, specific amino acids within this region responsible for the encapsidation of the genomic RNA have been identified. The region that is responsible for nucleocapsid core accumulation has considerable overlap with the region that controls encapsidation specificity.
    MeSH term(s) Amino Acid Sequence/physiology ; Capsid Proteins/genetics ; Capsid Proteins/physiology ; Genome, Viral ; Mutation ; Nucleocapsid ; RNA, Viral ; Sindbis Virus/physiology ; Virus Assembly
    Chemical Substances Capsid Proteins ; RNA, Viral
    Language English
    Publishing date 2008-02-27
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 80174-4
    ISSN 1098-5514 ; 0022-538X
    ISSN (online) 1098-5514
    ISSN 0022-538X
    DOI 10.1128/JVI.01936-07
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article: Tetrahymena POT1a regulates telomere length and prevents activation of a cell cycle checkpoint.

    Jacob, Naduparambil K / Lescasse, Rachel / Linger, Benjamin R / Price, Carolyn M

    Molecular and cellular biology

    2007  Volume 27, Issue 5, Page(s) 1592–1601

    Abstract: The POT1/TEBP telomere proteins are a group of single-stranded DNA (ssDNA)-binding proteins that have long been assumed to protect the G overhang on the telomeric 3' strand. We have found that the Tetrahymena thermophila genome contains two POT1 gene ... ...

    Abstract The POT1/TEBP telomere proteins are a group of single-stranded DNA (ssDNA)-binding proteins that have long been assumed to protect the G overhang on the telomeric 3' strand. We have found that the Tetrahymena thermophila genome contains two POT1 gene homologs, POT1a and POT1b. The POT1a gene is essential, but POT1b is not. We have generated a conditional POT1a cell line and shown that POT1a depletion results in a monster cell phenotype and growth arrest. However, G-overhang structure is essentially unchanged, indicating that POT1a is not required for overhang protection. In contrast, POT1a is required for telomere length regulation. After POT1a depletion, most telomeres elongate by 400 to 500 bp, but some increase by up to 10 kb. This elongation occurs in the absence of further cell division. The growth arrest caused by POT1a depletion can be reversed by reexpression of POT1a or addition of caffeine. Thus, POT1a is required to prevent a cell cycle checkpoint that is most likely mediated by ATM or ATR (ATM and ATR are protein kinases of the PI-3 protein kinase-like family). Our findings indicate that the essential function of POT1a is to prevent a catastrophic DNA damage response. This response may be activated when nontelomeric ssDNA-binding proteins bind and protect the G overhang.
    MeSH term(s) Alleles ; Animals ; Caffeine/pharmacology ; Cell Cycle ; Cell Line ; Chromatin Immunoprecipitation ; Genes, Essential ; Genes, Protozoan ; Genes, cdc ; Protozoan Proteins/genetics ; Protozoan Proteins/metabolism ; Telomere/genetics ; Telomere/metabolism ; Tetrahymena/genetics ; Tetrahymena/growth & development
    Chemical Substances Protozoan Proteins ; Caffeine (3G6A5W338E)
    Language English
    Publishing date 2007-03
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 779397-2
    ISSN 1098-5549 ; 0270-7306
    ISSN (online) 1098-5549
    ISSN 0270-7306
    DOI 10.1128/MCB.01975-06
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article: Sindbis virus nucleocapsid assembly: RNA folding promotes capsid protein dimerization.

    Linger, Benjamin R / Kunovska, Lyudmyla / Kuhn, Richard J / Golden, Barbara L

    RNA (New York, N.Y.)

    2003  Volume 10, Issue 1, Page(s) 128–138

    Abstract: In Sindbis virus, initiation of nucleocapsid core assembly begins with recognition of the encapsidation signal of the viral RNA genome by capsid protein. This nucleation event drives the recruitment of additional capsid proteins to fully encapsidate the ... ...

    Abstract In Sindbis virus, initiation of nucleocapsid core assembly begins with recognition of the encapsidation signal of the viral RNA genome by capsid protein. This nucleation event drives the recruitment of additional capsid proteins to fully encapsidate the genome, generating an icosahedral nucleocapsid core. The encapsidation signal of the Sindbis virus genomic RNA has previously been localized to a 132-nucleotide region of the genome within the coding region of the nsP1 protein, and the RNA-binding activity of the capsid was previously mapped to a central region of the capsid protein. It is unknown how capsid protein binding to encapsidation signal leads to ordered oligomerization of capsid protein and nucleocapsid core assembly. To address this question, we have developed a mobility shift assay to study this interaction. We have characterized a 32 amino acid peptide capable of recognizing the Sindbis virus encapsidation signal RNA. Using this peptide, we were able to observe a conformational change in the RNA induced by capsid protein binding. Binding is tight (K(d)(app) = 12 nM), and results in dimerization of the capsid peptide. Mutational analysis reveals that although almost every predicted secondary structure within the encapsidation signal is required for efficient protein binding, the identities of the bases within the helices and hairpin turns of the RNA do not need to be maintained. In contrast, two purine-rich loops are essential for binding. From these data, we have developed a model in which the encapsidation signal RNA adopts a highly folded structure and this folding process directs early events in nucleocapsid assembly.
    MeSH term(s) Base Pairing ; Base Sequence ; Binding Sites ; Dimerization ; Electrophoretic Mobility Shift Assay ; Genome, Viral ; Molecular Sequence Data ; Mutagenesis, Site-Directed ; Nucleic Acid Conformation ; Nucleocapsid/chemistry ; Nucleocapsid/metabolism ; Peptide Fragments/metabolism ; Protein Binding ; Protein Conformation ; Protein Folding ; Purines/metabolism ; RNA, Viral/genetics ; RNA, Viral/metabolism ; Sindbis Virus/physiology ; Viral Nonstructural Proteins/genetics ; Viral Nonstructural Proteins/metabolism ; Virus Assembly
    Chemical Substances Peptide Fragments ; Purines ; RNA, Viral ; Viral Nonstructural Proteins ; nsP1 protein, Sindbis virus
    Language English
    Publishing date 2003-12-15
    Publishing country United States
    Document type Comparative Study ; Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, P.H.S.
    ZDB-ID 1241540-6
    ISSN 1355-8382
    ISSN 1355-8382
    DOI 10.1261/rna.5127104
    Database MEDical Literature Analysis and Retrieval System OnLINE

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