scholarly journals A heterochromatin domain forms gradually at a new telomere and is highly dynamic at stable telomeres

2017 ◽  
Author(s):  
Jinyu Wang ◽  
Jessica R Eisenstatt ◽  
Julien Audry ◽  
Kristen Cornelius ◽  
Matthew Shaughnessy ◽  
...  

AbstractHeterochromatin domains play important roles in chromosome biology, organismal development and aging. In the fission yeast Schizosaccharomyces pombe and metazoans, heterochromatin is marked by histone H3 lysine 9 dimethylation. While factors required for heterochromatin have been identified, the dynamics of heterochromatin formation are poorly understood. Telomeres convert adjacent chromatin into heterochromatin. To form a new heterochromatic region in S. pombe, an inducible DNA double-strand break (DSB) was engineered next to 48 bp of telomere repeats in euchromatin, which caused formation of new telomere and gradual spreading of heterochromatin. However, spreading was highly dynamic even after the telomere had reached its stable length. The system also revealed the presence of repeats located at the boundaries of euchromatin and heterochromatin that are oriented to allow the efficient healing of a euchromatic DSB to cap the chromosome end with a new telomere. Telomere formation in S. pombe therefore reveals novel aspects of heterochromatin dynamics and the presence of failsafe mechanisms to repair subtelomeric breaks, with implications for similar processes in metazoan genomes.


2018 ◽  
Vol 38 (15) ◽  
Author(s):  
Jinyu Wang ◽  
Jessica R. Eisenstatt ◽  
Julien Audry ◽  
Kristen Cornelius ◽  
Matthew Shaughnessy ◽  
...  

ABSTRACTHeterochromatin domains play important roles in chromosome biology, organismal development, and aging, including centromere function, mammalian female X chromosome inactivation, and senescence-associated heterochromatin foci. In the fission yeastSchizosaccharomyces pombeand metazoans, heterochromatin contains histone H3 that is dimethylated at lysine 9. While factors required for heterochromatin have been identified, the dynamics of heterochromatin formation are poorly understood. Telomeres convert adjacent chromatin into heterochromatin. To form a new heterochromatic region inS. pombe, an inducible DNA double-strand break (DSB) was engineered next to 48 bp of telomere repeats in euchromatin, which caused formation of a new telomere and the establishment and gradual spreading of a new heterochromatin domain. However, spreading was dynamic even after the telomere had reached its stable length, with reporter genes within the heterochromatin domain showing variegated expression. The system also revealed the presence of repeats located near the boundaries of euchromatin and heterochromatin that are oriented to allow the efficient healing of a euchromatic DSB to cap the chromosome end with a new telomere. Telomere formation inS. pombetherefore reveals novel aspects of heterochromatin dynamics and fail-safe mechanisms to repair subtelomeric breaks, with implications for similar processes in metazoan genomes.



2004 ◽  
Vol 165 (6) ◽  
pp. 759-765 ◽  
Author(s):  
Creighton T. Tuzon ◽  
Britta Borgstrom ◽  
Dietmar Weilguny ◽  
Richard Egel ◽  
Julia Promisel Cooper ◽  
...  

Telomeres share the ability to silence nearby transcription with heterochromatin, but the requirement of heterochromatin proteins for most telomere functions is unknown. The fission yeast Rik1 protein is required for heterochromatin formation at centromeres and the mating-type locus, as it recruits the Clr4 histone methyltransferase, whose modification of histone H3 triggers binding by Swi6, a conserved protein involved in spreading of heterochromatin. Here, we demonstrate that Rik1 and Clr4, but not Swi6, are required along with the telomere protein Taz1 for crucial chromosome movements during meiosis. However, Rik1 is dispensable for the protective roles of telomeres in preventing chromosome end-fusion. Thus, a Swi6-independent heterochromatin function distinct from that at centromeres and the mating-type locus operates at telomeres during sexual differentiation.



eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Alessandro Stirpe ◽  
Nora Guidotti ◽  
Sarah J Northall ◽  
Sinan Kilic ◽  
Alexandre Hainard ◽  
...  

The SUV39 class of methyltransferase enzymes deposits histone H3 lysine 9 di- and trimethylation (H3K9me2/3), the hallmark of constitutive heterochromatin. How these enzymes are regulated to mark specific genomic regions as heterochromatic is poorly understood. Clr4 is the sole H3K9me2/3 methyltransferase in the fission yeast Schizosaccharomyces pombe, and recent evidence suggests that ubiquitination of lysine 14 on histone H3 (H3K14ub) plays a key role in H3K9 methylation. However, the molecular mechanism of this regulation and its role in heterochromatin formation remain to be determined. Our structure-function approach shows that the H3K14ub substrate binds specifically and tightly to the catalytic domain of Clr4, and thereby stimulates the enzyme by over 250-fold. Mutations that disrupt this mechanism lead to a loss of H3K9me2/3 and abolish heterochromatin silencing similar to clr4 deletion. Comparison with mammalian SET domain proteins suggests that the Clr4 SET domain harbors a conserved sensor for H3K14ub, which mediates licensing of heterochromatin formation.



2002 ◽  
Vol 22 (10) ◽  
pp. 3537-3548 ◽  
Author(s):  
Takashi Morishita ◽  
Yasuhiro Tsutsui ◽  
Hiroshi Iwasaki ◽  
Hideo Shinagawa

ABSTRACT To identify novel genes involved in DNA double-strand break (DSB) repair, we previously isolated Schizosaccharomyces pombe mutants which are hypersensitive to methyl methanesulfonate (MMS) and synthetic lethals with rad2. This study characterizes one of these mutants, rad60-1. The gene that complements the MMS sensitivity of this mutant was cloned and designated rad60. rad60 encodes a protein with 406 amino acids which has the conserved ubiquitin-2 motif found in ubiquitin family proteins. rad60-1 is hypersensitive to UV and γ rays, epistatic to rhp51, and defective in the repair of DSBs caused by γ-irradiation. The rad60-1 mutant is also temperature sensitive for growth. At the restrictive temperature (37°C), rad60-1 cells grow for several divisions and then arrest with 2C DNA content; the arrested cells accumulate DSBs and have a diffuse and often aberrantly shaped nuclear chromosomal domain. The rad60-1 mutant is a synthetic lethal with rad18-X, and expression of wild-type rad60 from a multicopy plasmid partially suppresses the MMS sensitivity of rad18-X cells. rad18 encodes a conserved protein of the structural maintenance of chromosomes (SMC) family (A. R. Lehmann, M. Walicka, D. J. Griffiths, J. M. Murray, F. Z. Watts, S. McCready, and A. M. Carr, Mol. Cell. Biol. 15:7067-7080, 1995). These results suggest that S. pombe Rad60 is required to repair DSBs, which accumulate during replication, by recombination between sister chromatids. Rad60 may perform this function in concert with the SMC protein Rad18.



2008 ◽  
Vol 28 (11) ◽  
pp. 3639-3651 ◽  
Author(s):  
Yufuko Akamatsu ◽  
Yasuto Murayama ◽  
Takatomi Yamada ◽  
Tomofumi Nakazaki ◽  
Yasuhiro Tsutsui ◽  
...  

ABSTRACT The Schizosaccharomyces pombe nip1 +/ctp1 + gene was previously identified as an slr (synthetically lethal with rad2) mutant. Epistasis analysis indicated that Nip1/Ctp1 functions in Rhp51-dependent recombinational repair, together with the Rad32 (spMre11)-Rad50-Nbs1 complex, which plays important roles in the early steps of DNA double-strand break repair. Nip1/Ctp1 was phosphorylated in asynchronous, exponentially growing cells and further phosphorylated in response to bleomycin treatment. Overproduction of Nip1/Ctp1 suppressed the DNA repair defect of an nbs1-s10 mutant, which carries a mutation in the FHA phosphopeptide-binding domain of Nbs1, but not of an nbs1 null mutant. Meiotic DNA double-strand breaks accumulated in the nip1/ctp1 mutant. The DNA repair phenotypes and epistasis relationships of nip1/ctp1 are very similar to those of the Saccharomyces cerevisiae sae2/com1 mutant, suggesting that Nip1/Ctp1 is a functional homologue of Sae2/Com1, although the sequence similarity between the proteins is limited to the C-terminal region containing the RHR motif. We found that the RxxL and CxxC motifs are conserved in Schizosaccharomyces species and in vertebrate CtIP, originally identified as a cofactor of the transcriptional corepressor CtBP. However, these two motifs are not found in other fungi, including Saccharomyces and Aspergillus species. We propose that Nip1/Ctp1 is a functional counterpart of Sae2/Com1 and CtIP.



Yeast ◽  
2012 ◽  
Vol 29 (7) ◽  
pp. 275-291 ◽  
Author(s):  
Sham Sunder ◽  
Nikole T. Greeson-Lott ◽  
Kurt W. Runge ◽  
Steven L. Sanders


2005 ◽  
Vol 4 (8) ◽  
pp. 1446-1454 ◽  
Author(s):  
Stephanie A. Morris ◽  
Yoichiro Shibata ◽  
Ken-ichi Noma ◽  
Yuko Tsukamoto ◽  
Erin Warren ◽  
...  

ABSTRACT Set2 methylation of histone H3 at lysine 36 (K36) has recently been shown to be associated with RNA polymerase II (Pol II) elongation in Saccharomyces cerevisiae. However, whether this modification is conserved and associated with transcription elongation in other organisms is not known. Here we report the identification and characterization of the Set2 ortholog responsible for K36 methylation in the fission yeast Schizosaccharomyces pombe. We find that similar to the budding yeast enzyme, S. pombe Set2 is also a robust nucleosome-selective H3 methyltransferase that is specific for K36. Deletion of the S. pombe set2 + gene results in complete abolishment of K36 methylation as well as a slow-growth phenotype on plates containing synthetic medium. These results indicate that Set2 is the sole enzyme responsible for this modification in fission yeast and is important for cell growth under stressed conditions. Using the chromatin immunoprecipitation assay, we demonstrate that K36 methylation in S. pombe is associated with the transcribed regions of Pol II-regulated genes and is devoid in regions that are not transcribed by Pol II. Consistent with a role for Set2 in transcription elongation, we find that S. pombe Set2 associates with the hyperphosphorylated form of Pol II and can fully rescue K36 methylation and Pol II interaction in budding yeast cells deleted for Set2. These results, along with our finding that K36 methylation is highly conserved among eukaryotes, imply a conserved role for this modification in the transcription elongation process.



2011 ◽  
Vol 195 (4) ◽  
pp. 563-572 ◽  
Author(s):  
Valerie C. Coffman ◽  
Pengcheng Wu ◽  
Mark R. Parthun ◽  
Jian-Qiu Wu

The stoichiometries of kinetochores and their constituent proteins in yeast and vertebrate cells were determined using the histone H3 variant CENP-A, known as Cse4 in budding yeast, as a counting standard. One Cse4-containing nucleosome exists in the centromere (CEN) of each chromosome, so it has been assumed that each anaphase CEN/kinetochore cluster contains 32 Cse4 molecules. We report that anaphase CEN clusters instead contained approximately fourfold more Cse4 in Saccharomyces cerevisiae and ∼40-fold more CENP-A (Cnp1) in Schizosaccharomyces pombe than predicted. These results suggest that the number of CENP-A molecules exceeds the number of kinetochore-microtubule (MT) attachment sites on each chromosome and that CENP-A is not the sole determinant of kinetochore assembly sites in either yeast. In addition, we show that fission yeast has enough Dam1–DASH complex for ring formation around attached MTs. The results of this study suggest the need for significant revision of existing CEN/kinetochore architectural models.



Author(s):  
Michael J. McKay ◽  
Peter van der Spek ◽  
Roland Kanaar ◽  
Bep Smit ◽  
Dirk Bootsma ◽  
...  


2018 ◽  
Vol 115 (40) ◽  
pp. E9333-E9342 ◽  
Author(s):  
Kyle R. Fowler ◽  
Randy W. Hyppa ◽  
Gareth A. Cromie ◽  
Gerald R. Smith

Viable gamete formation requires segregation of homologous chromosomes connected, in most species, by cross-overs. DNA double-strand break (DSB) formation and the resulting cross-overs are regulated at multiple levels to prevent overabundance along chromosomes. Meiotic cells coordinate these events between distant sites, but the physical basis of long-distance chromosomal communication has been unknown. We show that DSB hotspots up to ∼200 kb (∼35 cM) apart form clusters via hotspot-binding proteins Rec25 and Rec27 in fission yeast. Clustering coincides with hotspot competition and interference over similar distances. Without Tel1 (an ATM tumor-suppressor homolog), DSB and crossover interference become negative, reflecting coordinated action along a chromosome. These results indicate that DSB hotspots within a limited chromosomal region and bound by their protein determinants form a clustered structure that, via Tel1, allows only one DSB per region. Such a “roulette” process within clusters explains the observed pattern of crossover interference in fission yeast. Key structural and regulatory components of clusters are phylogenetically conserved, suggesting conservation of this vital regulation. Based on these observations, we propose a model and discuss variations in which clustering and competition between DSB sites leads to DSB interference and in turn produces crossover interference.



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