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Centromeric localization of dispersed Pol III genes in fission yeast.

ABSTRACT: The eukaryotic genome is a complex three-dimensional entity residing in the nucleus. We present evidence that Pol III-transcribed genes such as tRNA and 5S rRNA genes can localize to centromeres and contribute to a global genome organization. Furthermore, we find that ectopic insertion of Pol III genes into a non-Pol III gene locus results in the centromeric localization of the locus. We show that the centromeric localization of Pol III genes is mediated by condensin, which interacts with the Pol III transcription machinery, and that transcription levels of the Pol III genes are negatively correlated with the centromeric localization of Pol III genes. This centromeric localization of Pol III genes initially observed in interphase becomes prominent during mitosis, when chromosomes are condensed. Remarkably, defective mitotic chromosome condensation by a condensin mutation, cut3-477, which reduces the centromeric localization of Pol III genes, is suppressed by a mutation in the sfc3 gene encoding the Pol III transcription factor TFIIIC subunit, sfc3-1. The sfc3-1 mutation promotes the centromeric localization of Pol III genes. Our study suggests there are functional links between the process of the centromeric localization of dispersed Pol III genes, their transcription, and the assembly of condensed mitotic chromosomes.

SUBMITTER: Iwasaki O

PROVIDER: S-EPMC2808234 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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Centromeric localization of dispersed Pol III genes in fission yeast.

Iwasaki Osamu O Tanaka Atsunari A Tanizawa Hideki H Grewal Shiv I S SI Noma Ken-Ichi K

Molecular biology of the cell 20091112 2

The eukaryotic genome is a complex three-dimensional entity residing in the nucleus. We present evidence that Pol III-transcribed genes such as tRNA and 5S rRNA genes can localize to centromeres and contribute to a global genome organization. Furthermore, we find that ectopic insertion of Pol III genes into a non-Pol III gene locus results in the centromeric localization of the locus. We show that the centromeric localization of Pol III genes is mediated by condensin, which interacts with the Po ...[more]

PMID: 19910488

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Project description:Centromeres are specialized chromatin regions marked by the presence of nucleosomes containing the centromere-specific histone H3 variant CENP-A, which is essential for chromosome segregation. Assembly and disassembly of nucleosomes is intimately linked to DNA topology and DNA topoisomerases have previously been implicated in the dynamics of canonical H3 nucleosomes. Here we show that Schizosaccharomyces pombe Top3 and its partner Rqh1 are involved in controlling the levels of CENP-ACnp1 at centromeres. Both top3 and rqh1 mutants display defects in chromosome segregation. Using chromatin immunoprecipitation and tiling microarrays we show that Top3 unlike Top1 and Top2 is highly enriched at centromeric central domains, demonstrating that Top3 is the major topoisomerase in this region. Moreover, centromeric Top3 occupancy positively correlates with CENP-ACnp1 occupancy. Intriguingly, both top3 and rqh1 mutants display increased relative enrichment of CENP-ACnp1 at centromeric central domains. Thus, Top3 and Rqh1 normally limit the levels of CENP-ACnp1 in this region. This new role is independent of the established function of Top3 and Rqh1 in homologous recombination downstream of Rad51. Therefore, we hypothesize that the Top3-Rqh1 complex has an important role in controlling centromere DNA topology which in turn affects the dynamics of CENP-ACnp1 nucleosomes. For transcription: Total RNA from top3-105 mutant and WT control cells after 8 hours at 36C in biological duplicates. For Top3-myc chromatin immunoprecipitation: DNA immunoprecipitated with mouse anti-Myc using chromatin extracts from cells expressing Top3-Myc from the endogenous locus at 30C in biological duplicates normalized to input DNA from wild type cells at 30C in biological duplicates. For CENP-A/Cnp1 chromatin immunoprecipitation: DNA immunoprecipitated with anti-Cnp1 serum using chromatin extracts from top3-105 mutant and wild type control cells after 8 hours at 36C in in biological duplicates normalized to input DNA from each strain.

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Centromeric localization of dispersed Pol III genes in fission yeast.

Publications

Centromeric localization of dispersed Pol III genes in fission yeast.

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