Differentiation of nuclear structure during the sexual cycle in Tetrahymena thermophila

Weiske-Benner, Annelie; Eckert, Werner A.

doi:10.1111/j.1432-0436.1985.tb00829.x

Cited by 21 publications

(30 citation statements)

References 55 publications

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“…Hhp1 remained in the macronucleus throughout its programmed degradation in conjugating cells (Fig. 3b), a process that involves extensive chromatin condensation (35). We found no evidence of its participation in micronuclear decondensation or recondensation during meiosis but found that it selectively marked postzygotic nuclei slated for macronuclear development very early in the differentiation process.…”

Section: Discussionmentioning

confidence: 99%

Phosphorylation-Dependent Targeting of Tetrahymena HP1 to Condensed Chromatin

Yale

Tackett

Neuman

et al. 2016

mSphere

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Compacting the genome to various degrees influences processes that use DNA as a template, such as gene transcription and replication. This project was aimed at learning more about the cellular mechanisms that control genome compaction. Posttranslational modifications of proteins involved in genome condensation are emerging as potentially important points of regulation. To help elucidate protein modifications and how they affect the function of condensation proteins, we investigated the phosphorylation of the chromatin protein called Hhp1 in the ciliated protozoan Tetrahymena thermophila. This is one of the first functional investigations of these modifications of a nonhistone chromatin condensation protein that acts on the ciliate genome, and discoveries will aid in identifying common, evolutionarily conserved strategies that control the dynamic compaction of genomes.

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Section: Discussionmentioning

confidence: 99%

Phosphorylation-Dependent Targeting of Tetrahymena HP1 to Condensed Chromatin

Yale

Tackett

Neuman

et al. 2016

mSphere

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“…1E shows that Hhp1p is not uniformly distributed within macronuclei. Previous ultrastructural analyses have shown that macronuclear chromatin also is not uniform with respect to the distribution of condensed and decondensed chromatin (23,33). The punctate staining exhibited by Hhp1p antisera suggested that Hhp1p might be enriched in electron-dense CBs that punctuate macronuclei (shown in the low magnification micrograph in Fig.…”

Section: Fig 4 Hhp1p Is Multiply Phosphorylated By Using Two Potentmentioning

confidence: 89%

An HP1-like protein is missing from transcriptionally silent micronuclei of Tetrahymena

Huang

Wiley

Lending

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

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We report the identification and cloning of a 28-kDa polypeptide (p28) in Tetrahymena macronuclei that shares several features with the well studied heterochromatinassociated protein HP1 from Drosophila. Notably, like HP1, p28 contains both a chromodomain and a chromoshadow domain. p28 also shares features with linker histone H1, and like H1, p28 is multiply phosphorylated, at least in part, by a proline-directed, Cdc2-type kinase. As such, p28 is referred to as Hhp1p (for H1͞HP1-like protein). Hhp1p is missing from transcriptionally silent micronuclei but is enriched in heterochromatin-like chromatin bodies that presumably comprise repressed chromatin in macronuclei. These findings shed light on the evolutionary conserved nature of heterochromatin in organisms ranging from ciliates to humans and provide further evidence that HP1-like proteins are not exclusively associated with permanently silent chromosomal domains. Our data support a view that members of this family also associate with repressed states of euchromatin.

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“…The observation that the three haploid meiotic products are also differentially stained by “apofluor” suggests that their elimination is also associated with acidification. It had been hypothesized, on the basis of electron microscopic observations, that both the dying macronucleus and the degrading haploid nuclei become enveloped by a lysosomally‐derived vacuole, forming autophagosomes (Weiske‐Benner and Eckert 1987). Our observations showing that dying nuclei stain with apofluor, indicating that they become acidified, supports that hypothesis.…”

Section: Discussionmentioning

confidence: 99%

Nuclear Death in Living Tetrahymena: The Case of the Haploid Nuclei

Santos

Wolfe

2000

J Eukaryotic Microbiology

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During sexual conjugation in Tetrahymena the micronucleus divides meiotically, producing four haploid nuclei. While one of these nuclei divides mitotically to yield two genetically identical gametic pronuclei, a stationary pronucleus and a migratory pronucleus, the remaining three haploid nuclei degenerate and disappear. Typically, they migrate to the posterior end of the cell where they remain as residual bodies until they disappear. In the present study we asked whether degenerating haploid nuclei share any properties with apoptotic nuclei. Specifically, we wondered whether they would be stained by "apofluor", a combination of vital fluorescent indicators that differentially stains apoptotic nuclei in living cells. "Apofluor" includes acridine orange, which becomes trapped in acidic compartments and stains lysosomal bodies a brilliant orange-red, and Hoechst 33342, which binds to DNA and stains nuclei bright blue. With this dye combination, while ordinary nuclei stain blue, the apoptotic macronucleus stains first blue-green, then yellow, and finally orange. The progression in color is presumed to be due to the accumulation of protons in the apoptotic nucleus compartment. We found that three of the four post-meiotic haploid nuclei, those that are eliminated, were stained differentially green, then yellow, and then come to be indistinguishable from the orange lysosomal bodies. Differential staining can occur even while the nuclei are located at the anterior ends of the cells, and before the "viable" nucleus divides to form pronuclei. These results indicate that haploid nuclei in the process of degradation are differentially stained in living cells by "apofluor", and that the differential staining occurs early in the elimination process. Further, since the degenerating haploid nuclei are stained by "apofluor" it is likely that they are degraded by a mechanism similar to the elimination of the apoptotic macronucleus.

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Differentiation of nuclear structure during the sexual cycle in Tetrahymena thermophila

Cited by 21 publications

References 55 publications

Phosphorylation-Dependent Targeting of Tetrahymena HP1 to Condensed Chromatin

Phosphorylation-Dependent Targeting of Tetrahymena HP1 to Condensed Chromatin

An HP1-like protein is missing from transcriptionally silent micronuclei of Tetrahymena

Nuclear Death in Living Tetrahymena: The Case of the Haploid Nuclei

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