scholarly journals LIA4Encodes a Chromoshadow Domain Protein Required for Genomewide DNA Rearrangements in Tetrahymena thermophila

2014 ◽  
Vol 13 (10) ◽  
pp. 1300-1311 ◽  
Author(s):  
Scott A. Horrell ◽  
Douglas L. Chalker
Keyword(s):  
Critical Role ◽  
Dna Rearrangement ◽  
Rnai Machinery ◽  
Content Type ◽  
Heterochromatin Formation ◽  
H3k27 Methylation ◽  
Dna Elimination ◽  
Somatic Genome ◽  
Subsequent Elimination ◽  
Elimination Pathway

ABSTRACTExtensive DNA elimination occurs as part of macronuclear differentiation duringTetrahymenasexual reproduction. The identification of sequences to excise is guided by a specialized RNA interference (RNAi) machinery that targets the methylation of histone H3 lysine 9 (K9) and K27 on chromatin associated with these internal eliminated sequences (IESs). This modified chromatin is reorganized into heterochromatic subnuclear foci, which is a hallmark of their subsequent elimination. Here, we demonstrate that Lia4, a chromoshadow domain-containing protein, is an essential component in this DNA elimination pathway.LIA4knockout (ΔLIA4) lines fail to excise IESs from their developing somatic genome and arrest at a late stage of conjugation. Lia4 acts after RNAi-guided heterochromatin formation, as both H3K9 and H3K27 methylation are established. Nevertheless, withoutLIA4, these cells fail to form the heterochromatic foci associated with DNA rearrangement, and Lia4 accumulates in the foci, indicating that Lia4 plays a key role in their structure. These data indicate a critical role for Lia4 in organizing the nucleus duringTetrahymenamacronuclear differentiation.

scholarly journals Tetrahymena thermophila JMJD3 Homolog Regulates H3K27 Methylation and Nuclear Differentiation

2012 ◽  
Vol 11 (5) ◽  
pp. 601-614 ◽  
Author(s):  
Pei-Han Chung ◽  
Meng-Chao Yao
Keyword(s):  
Gene Expression ◽  
Tetrahymena Thermophila ◽  
Critical Role ◽  
Content Type ◽  
Chromatin Dynamics ◽  
H3k27 Methylation ◽  
Dna Elimination ◽  
Severe Reduction ◽  
Nuclear Development ◽  
Important Regulator

ABSTRACT Histone H3K27me3 modification is an important regulator for development and gene expression. In Tetrahymena thermophila , the complex chromatin dynamics of H3K27me3 marks during nuclear development suggested that an H3K27me3 demethylase might exist. Here, we report an H3K27me3 demethylase homolog, JMJ1 , in Tetrahymena . During conjugation, JMJ1 expression is upregulated and the protein is localized first in the parental macronucleus and then in the new macronucleus. In conjugating cells, knockdown of JMJ1 expression resulted in a severe reduction in the production of progeny, suggesting that JMJ1 is essential for Tetrahymena conjugation. Furthermore, knockdown of JMJ1 resulted in increased H3K27 trimethylation in the new macronucleus and reduced transcription of genes related to DNA elimination, while the DNA elimination process was also partially blocked. Knockdown of the H3K27 methyltransferase EZL2 but not that of EZL1 partially restored progeny production in JMJ1 -knockdown cells and reduced abnormal H3K27me3 accumulation in the new macronucleus. Taken together, these results demonstrate a critical role for JMJ1 in regulating H3K27me3 during conjugation and the importance of JMJ1 in regulating gene expression in the new macronucleus but not in regulating the formation of heterochromatin associated with programmed DNA deletion.

scholarly journals Ccq1p and the Condensin Proteins Cut3p and Cut14p Prevent Telomere Entanglements in the Fission Yeast Schizosaccharomyces pombe

2010 ◽  
Vol 9 (10) ◽  
pp. 1612-1621 ◽  
Author(s):  
Tina Motwani ◽  
Rosemarie Doris ◽  
Scott G. Holmes ◽  
Mark R. Flory
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Affinity Purification ◽  
Critical Role ◽  
Loss Of Function ◽  
Checkpoint Activation ◽  
Content Type ◽  
High Frequencies ◽  
Heterochromatin Formation ◽  
Length Regulation ◽  
Telomere Length Regulation

ABSTRACT The Schizosaccharomyces pombe telomere-associated protein Ccq1p has previously been shown to participate in telomerase recruitment, heterochromatin formation, and suppression of checkpoint activation. Here we characterize a critical role for Ccq1p in mitotic transit. We show that mitotic cells lacking Ccq1p lose minichromosomes at high frequencies but that conditional knockdown of Ccq1p expression results in telomere bridging within one cell cycle. Elevating Ccq1p expression resolves the telomere entanglements caused by decreased Taz1p activity. Ccq1p affects telomere resolution in the absence of changes in telomere size, indicating a role for Ccq1p that is independent of telomere length regulation. Using affinity purification, we identify the condensin proteins Cut3p and Cut14p as candidate Ccq1p interactors in this activity. Condensin loss-of-function disrupts Ccq1p telomeric localization and normal intertelomere clustering, while condensin overexpression relieves the chromosome segregation defects associated with conditional Ccq1p knockdown. These data suggest that Ccq1p and condensins collaborate to mediate resolution of telomeres in mitosis and regulate intertelomeric clustering during interphase.

scholarly journals Two GW Repeat Proteins Interact with Tetrahymena thermophila Argonaute and Promote Genome Rearrangement

2009 ◽  
Vol 29 (18) ◽  
pp. 5020-5030 ◽  
Author(s):  
Janna Bednenko ◽  
Tomoko Noto ◽  
Leroi V. DeSouza ◽  
K. W. Michael Siu ◽  
Ronald E. Pearlman ◽  
...  
Keyword(s):  
Genome Rearrangement ◽  
Developmental Stages ◽  
Tetrahymena Thermophila ◽  
Germ Line ◽  
Nuclear Bodies ◽  
Interacting Proteins ◽  
Heterochromatin Formation ◽  
Dna Elimination ◽  
Somatic Genome ◽  
Argonaute Family

ABSTRACT In conjugating Tetrahymena thermophila, massive DNA elimination occurs upon the development of the new somatic genome from the germ line genome. Small, ∼28-nucleotide scan RNAs (scnRNAs) and Twi1p, an Argonaute family member, mediate H3K27me3 and H3K9me3 histone H3 modifications, which lead to heterochromatin formation and the excision of the heterochromatinized germ line-limited sequences. In our search for new factors involved in developmental DNA rearrangement, we identified two Twi1p-interacting proteins, Wag1p and CnjBp. Both proteins contain GW (glycine and tryptophan) repeats, which are characteristic of several Argonaute-interacting proteins in other organisms. Wag1p and CnjBp colocalize with Twi1p in the parental macronucleus early in conjugation and in the new developing macronucleus during later developmental stages. Around the time DNA elimination occurs, Wag1p forms multiple nuclear bodies in the developing macronuclei that do not colocalize with heterochromatic DNA elimination structures. Analyses of ΔWAG1, ΔCnjB, and double ΔWAG1 ΔCnjB knockout strains revealed that WAG1 and CnjB genes need to be deleted together to inhibit the downregulation of specific scnRNAs, the formation of DNA elimination structures, and DNA excision. Thus, Wag1p and CnjBp are two novel players with overlapping functions in RNA interference-mediated genome rearrangement in Tetrahymena.

scholarly journals RNAi-dependent H3K27 methylation is required for heterochromatin formation and DNA elimination in Tetrahymena

2007 ◽  
Vol 21 (12) ◽  
pp. 1530-1545 ◽  
Author(s):  
Y. Liu ◽  
S. D. Taverna ◽  
T. L. Muratore ◽  
J. Shabanowitz ◽  
D. F. Hunt ◽  
...  
Keyword(s):  
Heterochromatin Formation ◽  
H3k27 Methylation ◽  
Dna Elimination

scholarly journals RNA-mediated nucleosome depletion is required for elimination of transposon-derived DNA.

2022 ◽  
Author(s):  
Aditi Singh ◽  
Xyrus X. Maurer-Alcalá ◽  
Therese Solberg ◽  
Silvan Gisler ◽  
Michael Ignarski ◽  
...  
Keyword(s):  
Transposable Elements ◽  
Chromatin Remodeling ◽  
Dna Cleavage ◽  
Small Rnas ◽  
Heterochromatin Formation ◽  
Dna Accessibility ◽  
Dna Elimination ◽  
Nucleosome Density ◽  
Somatic Genome ◽  
Genomic Regions

Small RNAs are known to mediate silencing of transposable elements and other genomic loci, increasing nucleosome density and preventing undesirable gene expression. Post-zygotic development of the Paramecium somatic genome requires elimination of thousands of transposon remnants (IESs) and transposable elements that are scattered throughout the germline genome (Garnier et al. 2004). The elimination process is guided by Piwi-associated small RNAs and leads to precise cleavage at IES boundaries (Bouhouche et al. 2011; Furrer et al. 2017). Previous research suggests that small RNAs induce heterochromatin formation within IESs, which, in turn, is required for DNA elimination (Liu et al. 2007). Here we show that IES recognition and precise excision is facilitated by recruitment of a homolog of a chromatin remodeler ISWI, which depletes target genomic regions of nucleosomes, making the chromatin accessible for DNA cleavage. ISWI knockdown in Paramecium leads to pronounced inhibition of DNA elimination. Furthermore, nucleosome profiling indicates that ISWI is required for IES elimination in nucleosome-dense genomic regions, while other IESs do not require small RNAs or ISWI for excision. ISWI silencing notably also reduces DNA elimination precision, resulting in aberrant excision at alternative IES boundaries. In summary, we demonstrate that chromatin remodeling that increases DNA accessibility together with small RNAs are necessary for efficient and precise DNA elimination in Paramecium.

scholarly journals RNA Interference in Fungi: Pathways, Functions, and Applications

2011 ◽  
Vol 10 (9) ◽  
pp. 1148-1155 ◽  
Author(s):  
Yunkun Dang ◽  
Qiuying Yang ◽  
Zhihong Xue ◽  
Yi Liu
Keyword(s):  
Gene Regulation ◽  
Rna Interference ◽  
Small Rna ◽  
Rnai Machinery ◽  
Content Type ◽  
Heterochromatin Formation ◽  
Rna Molecules ◽  
Cellular Processes ◽  
Rna Biogenesis ◽  
Core Components

ABSTRACT Small RNA molecules of about 20 to 30 nucleotides function in gene regulation and genomic defense via conserved eukaryotic RNA interference (RNAi)-related pathways. The RNAi machinery consists of three core components: Dicer, Argonaute, and RNA-dependent RNA polymerase. In fungi, the RNAi-related pathways have three major functions: genomic defense, heterochromatin formation, and gene regulation. Studies of Schizosaccharomyces pombe and Neurospora , and other fungi have uncovered surprisingly diverse small RNA biogenesis pathways, suggesting that fungi utilize RNAi-related pathways in various cellular processes to adapt to different environmental conditions. These studies also provided important insights into how RNAi functions in eukaryotic systems in general. In this review, we will discuss our current understanding of the fungal RNAi-related pathways and their functions, with a focus on filamentous fungi. We will also discuss how RNAi can be used as a tool in fungal research.

Accessing resources for service innovation – the critical role of network relationships

2014 ◽  
Vol 25 (1) ◽  
pp. 2-29 ◽  
Author(s):  
Helena Rusanen ◽  
Aino Halinen ◽  
Elina Jaakkola
Keyword(s):  
Critical Role ◽  
Service Innovation ◽  
Innovation Process ◽  
Research Strategy ◽  
Future Research ◽  
Theoretical Understanding ◽  
Resource Access ◽  
Content Type ◽  
External Resources ◽  
Different Types

Purpose – This paper aims to explore how companies access resources through network relationships when developing service innovations. The paper identifies the types of resource that companies seek from other actors and examines the nature of relationships and resource access strategies that can be applied to access each type of resource. Design/methodology/approach – A longitudinal, multi-case study is conducted in the field of technical business-to-business (b-to-b) services. An abductive research strategy is applied to create a new theoretical understanding of resource access. Findings – Companies seek a range of resources through different types of network relationships for service innovation. Four types of resource access strategies were identified: absorption, acquisition, sharing, and co-creation. The findings show how easily transferable resources can be accessed through weak relationships and low-intensity collaboration. Access to resources that are difficult to transfer, instead, necessitates strong relationships and high-intensity collaboration. Research limitations/implications – The findings are valid for technical b-to-b services, but should also be tested for other kinds of innovations. Future research should also study how actors integrate the resources gained through networks in the innovation process. Practical implications – Managers should note that key resources for service innovation may be accessible through a variety of actors and relationships ranging from formal arrangements to miscellaneous social contacts. To make use of tacit resources such as knowledge, firms need to engage in intensive collaboration. Originality/value – Despite attention paid to network relationships, innovation collaboration, and external resources, previous research has neither linked these issues nor studied their mutual contingencies. This paper provides a theoretical model that characterizes the service innovation resources accessible through different types of relationships and access strategies.

scholarly journals A Developmentally Regulated Gene, ASI2, Is Required for Endocycling in the Macronuclear Anlagen of Tetrahymena

2010 ◽  
Vol 9 (9) ◽  
pp. 1343-1353 ◽  
Author(s):  
Lihui Yin ◽  
Susan T. Gater ◽  
Kathleen M. Karrer
Keyword(s):  
Signal Transduction ◽  
Mitotic Cycle ◽  
Tetrahymena Thermophila ◽  
Germ Line ◽  
Ciliated Protozoa ◽  
Dna Rearrangement ◽  
Developmentally Regulated ◽  
Content Type ◽  
Molecular Events ◽  
Multicellular Organisms

ABSTRACT Ciliated protozoa contain two types of nuclei, germ line micronuclei (Mic) and transcriptionally active macronuclei (Mac). During sexual reproduction, the parental Mac degenerates and a new Mac develops from a mitotic product of the zygotic Mic. Macronuclear development involves extensive endoreplication of the genome. The present study shows that endoreplication of macronuclear DNA in Tetrahymena is an example of endocyling, a variant of the mitotic cycle with alternating S and G phases in the absence of cell division. Thus, endocycling is conserved from ciliates to multicellular organisms. The gene ASI2 in Tetrahymena thermophila encodes a putative signal transduction receptor. ASI2 is nonessential for vegetative growth, but it is upregulated during development of the new Mac. Cells that lack ASI2 in the developing Mac anlagen are arrested in endoreplication of the DNA and die. This study shows that ASI2 is also transcribed in the parental Mac early in conjugation and that transcription of ASI2 in the parental Mac supports endoreplication of the DNA during early stages of development of the Mac anlagen. Other molecular events in Mac anlage development, including developmentally regulated DNA rearrangement, occur normally in matings between ASI2 knockouts, suggesting that ASI2 specifically regulates endocycling in Tetrahymena.

Healthcare supply chain management: literature review and some issues

2018 ◽  
Vol 15 (3) ◽  
pp. 265-287 ◽  
Author(s):  
Bhavana Mathur ◽  
Sumit Gupta ◽  
Makhan Lal Meena ◽  
G.S. Dangayach
Keyword(s):  
Supply Chain ◽  
Supply Chain Management ◽  
Literature Review ◽  
Organizational Performance ◽  
Critical Role ◽  
Sample Survey ◽  
Future Research ◽  
Chain Management ◽  
Content Type ◽  
Potential Benefits

PurposeThe purpose of this paper is to examine the causal linkages among supply chain practices, effectiveness of supply chain performance (SCP) and organizational performance (OP) in Indian healthcare industries.Design/methodology/approachThis paper is helpful in developing a framework for linking a healthcare supply chain practice to its OP, and thus identifies how such a linkage can be connected to the effectiveness of SCP. Such effort also enables the authors to derive a set of recommended supply chain practices for SC performance.FindingsFrom the literature review, this paper finds that, in the context of Indian healthcare industries, efficient SC performance may play a critical role for overall OP improvement, as there is a close interrelationship between supply chain management (SCM) practices and SCP that may have a more significant effect on OP improvement.Research limitations/implicationsThe principle limitation of the paper is that it is performed only in a particular industry and with a questionnaire survey which could be extended in future for other industries also. Another limitation of the paper is that it is focused only on the SCP of medical device and equipment supply chain which is a small portion of the whole healthcare supply chain, and therefore requires further research covering various other domains of healthcare supply chain. Another limitation of the study is that the sample survey has been taken from only one respondent per company at one point of time which may create biasness in the results. Thus, future research should collect data through multiple members from the organization.Practical implicationsThis study contributes to know the effect of SCM practices on healthcare SCP and provides a practical and useful tool to evaluate the extent of effectiveness of SCP and finally their impact on the healthcare OP. Finally, this study provides conceptual and descriptive literature regarding SCM practices that leads to improvement in healthcare performance.Social implicationsThis study adds to the knowledge on healthcare SCM performance by exploring the relationship between supply chain practices, healthcare SCP and healthcare OP and by developing and testing a research framework thus help in improving patient satisfaction.Originality/valueThis study attempts to show how the potential benefits of supply chain practices can no longer be ignored in healthcare supply chain.

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