Abstract
Vegetative cells of the ciliated protozoan Tetrahymena thermophila contain a transcriptionally active macronucleus and a transcriptionally inactive micronucleus. Earlier studies ( Allis , C. D., C. V. C. Glover , J. K. Bowen, and M. A. Gorovsky , 1980, Cell, 20:609-617; and Allis , C. D., Y. S. Ziegler , M. A. Gorovsky , and J. B. Olmsted, 1982, Cell, 31:131-136) demonstrated the existence of a macronuclear-specific histone variant, hv1 , which is enriched in small punctate regions in nucleoli of several mammalian cell lines. These observations suggest that this histone variant is highly conserved in evolution and may be associated with actively transcribed sequences. Despite large differences in structure and function during vegetative growth, macro- and micronuclei are related. During conjugation, the sexual phase of the life cycle in Tetrahymena, postzygotic division products of micronuclei give rise to new micro- and macronuclei, while the old macronucleus moves to the posterior of each cell and is eliminated. In this study using antiserum specific for hv1 , we determined by indirect immunofluorescence the time during conjugation at which hv1 first appears in the developing new macronuclei. In growing, starved, and young mating cells (2-5 h after mixing opposite mating types), only macronuclei are detected with affinity-purified antibodies against hv1 . Newly formed macronuclei are either not stained or only weakly stained in cells in which the old macronucleus is located in the center of the cell. However, new macronuclei are clearly observed in cells in which the old macronucleus has moved to the posterior of the cell (approximately 8 h). During later stages of conjugation (10-16 h), the intensity of hv1 staining in new macronuclei increases with time corresponding to the increasing DNA content of these nuclei. Disappearance of detectable hv1 from old macronuclei begins nearly 1 h after these nuclei reach the posterior cytoplasm (approximately 9-10 h) and is sometimes complete before these nuclei are eliminated from the cells. Autoradiography of cells labeled for brief periods with [3H]uridine shows that new macronuclei begin to synthesize RNA very soon after the second postzygotic division (approximately 8 h). During stages when hv1 is clearly detected in new macronuclei, anlagen are active in RNA synthesis. RNA synthesis in old macronuclei ceases very close to the time when RNA synthesis begins in new macronuclei. Thus, the addition of hv1 coincides closely with the transformation of a transcriptionally inactive germinal nucleus into that of a transcriptionally active somatic nucleus. We suspect that addition of hv1 plays a fundamental role in
Full Text
The Full Text of this article is available as a PDF (3.8 MB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Allis C. D., Dennison D. K. Identification and purification of young macronuclear anlagen from conjugating cells of Tetrahymena thermophila. Dev Biol. 1982 Oct;93(2):519–533. doi: 10.1016/0012-1606(82)90139-7. [DOI] [PubMed] [Google Scholar]
- Allis C. D., Glover C. V., Bowen J. K., Gorovsky M. A. Histone variants specific to the transcriptionally active, amitotically dividing macronucleus of the unicellular eucaryote, Tetrahymena thermophila. Cell. 1980 Jul;20(3):609–617. doi: 10.1016/0092-8674(80)90307-4. [DOI] [PubMed] [Google Scholar]
- Allis C. D., Wiggins J. C. Histone rearrangements accompany nuclear differentiation and dedifferentiation in Tetrahymena. Dev Biol. 1984 Feb;101(2):282–294. doi: 10.1016/0012-1606(84)90142-8. [DOI] [PubMed] [Google Scholar]
- Allis C. D., Ziegler Y. S., Gorovsky M. A., Olmsted J. B. A conserved histone variant enriched in nucleoli of mammalian cells. Cell. 1982 Nov;31(1):131–136. doi: 10.1016/0092-8674(82)90412-3. [DOI] [PubMed] [Google Scholar]
- Bruns P. J., Brussard T. B. Pair formation in tetrahymena pyriformis, an inducible developmental system. J Exp Zool. 1974 Jun;188(3):337–344. doi: 10.1002/jez.1401880309. [DOI] [PubMed] [Google Scholar]
- Gorovsky M. A. Macro- and micronuclei of Tetrahymena pyriformis: a model system for studying the structure and function of eukaryotic nuclei. J Protozool. 1973 Feb;20(1):19–25. doi: 10.1111/j.1550-7408.1973.tb05995.x. [DOI] [PubMed] [Google Scholar]
- Gorovsky M. A., Yao M. C., Keevert J. B., Pleger G. L. Isolation of micro- and macronuclei of Tetrahymena pyriformis. Methods Cell Biol. 1975;9(0):311–327. doi: 10.1016/s0091-679x(08)60080-1. [DOI] [PubMed] [Google Scholar]
- Johmann C. A., Gorovsky M. A. Immunofluorescence evidence for the absence of histone H1 in a mitotically dividing, genetically inactive nucleus. J Cell Biol. 1976 Oct;71(1):89–95. doi: 10.1083/jcb.71.1.89. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mackay S., Newrock K. M. Histone subtypes and switches in synthesis of histone subtypes during Ilyanassa development. Dev Biol. 1982 Oct;93(2):430–437. doi: 10.1016/0012-1606(82)90130-0. [DOI] [PubMed] [Google Scholar]
- Martindale D. W., Allis C. D., Bruns P. J. Conjugation in Tetrahymena thermophila. A temporal analysis of cytological stages. Exp Cell Res. 1982 Jul;140(1):227–236. doi: 10.1016/0014-4827(82)90172-0. [DOI] [PubMed] [Google Scholar]
- Newrock K. M., Alfageme C. R., Nardi R. V., Cohen L. H. Histone changes during chromatin remodeling in embryogenesis. Cold Spring Harb Symp Quant Biol. 1978;42(Pt 1):421–431. doi: 10.1101/sqb.1978.042.01.045. [DOI] [PubMed] [Google Scholar]
- Olmsted J. B. Affinity purification of antibodies from diazotized paper blots of heterogeneous protein samples. J Biol Chem. 1981 Dec 10;256(23):11955–11957. [PubMed] [Google Scholar]
- Simpson R. T. Modulation of nucleosome structure by histone subtypes in sea urchin embryos. Proc Natl Acad Sci U S A. 1981 Nov;78(11):6803–6807. doi: 10.1073/pnas.78.11.6803. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Vavra K. J., Allis C. D., Gorovsky M. A. Regulation of histone acetylation in Tetrahymena macro- and micronuclei. J Biol Chem. 1982 Mar 10;257(5):2591–2598. [PubMed] [Google Scholar]