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Cell division in higher plants: a cdc2 gene, its 34-kDa product, and histone H1 kinase activity in pea.

ABSTRACT: The mitotic cell cycle of yeast and animal cells is regulated by the cdc2 gene and its product, the p34 protein kinase, and by other components of the MPF or histone H1 kinase complex. We present evidence that cdc2, p34, and a histone H1 kinase also exist in higher plants. Protein extracts from 10 plant species surveyed display a 34-kDa component recognized by a monoclonal antibody directed against an evolutionarily conserved epitope of fission yeast p34. Nondenatured protein extracts of mitotic Pisum sativum (garden pea) tissues were fractionated by gel filtration, electrophoretically separated under denaturing conditions, and immunoblotted. p34 crossreactive material was apparent in both low and high molecular mass fractions, indicating that pea p34 occurs as both a monomer and as part of a high molecular mass complex. Histone H1 kinase activity was found predominantly in the higher molecular mass fractions, those to which the least phosphorylated form of pea p34 was confined. We also report the cloning of the pea homologue of cdc2 by polymerase chain reaction. DNA sequence analysis reveals perfect conservation of the hallmark "PSTAIR" sequence motif found in all cdc2 gene products analyzed to date.

SUBMITTER: Feiler HS

PROVIDER: S-EPMC54331 | biostudies-other | 1990 Jul

REPOSITORIES: biostudies-other

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Cell division in higher plants: a cdc2 gene, its 34-kDa product, and histone H1 kinase activity in pea.

Feiler H S HS Jacobs T W TW

Proceedings of the National Academy of Sciences of the United States of America 19900701 14

The mitotic cell cycle of yeast and animal cells is regulated by the cdc2 gene and its product, the p34 protein kinase, and by other components of the MPF or histone H1 kinase complex. We present evidence that cdc2, p34, and a histone H1 kinase also exist in higher plants. Protein extracts from 10 plant species surveyed display a 34-kDa component recognized by a monoclonal antibody directed against an evolutionarily conserved epitope of fission yeast p34. Nondenatured protein extracts of mitotic ...[more]

PMID: 2164683

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Project description:Chromatin dynamics can regulate all DNA-dependent processes. Access to DNA within chromatin is orchestrated mainly by histones and their posttranslational modifications (PTMs). Like other eukaryotes, the apicomplexan parasite Toxoplasma gondii encodes four canonical histones and five histone variants. In contrast, the linker histone (H1) has never been identified in apicomplexan parasites. In other eukaryotes, histone H1 compacts the chromatin by linking the nucleosome and increasing the DNA compaction. H1 is a multifunctional protein and can be involved in different steps of DNA metabolism or associated with protein complexes related to distinct biological processes. We have identified a novel protein in T. gondii ("TgH1-like") that, although lacking the globular domain of mammalian H1, is remarkably like the H1-like proteins of bacteria and trypanosomatids. Our results demonstrate that TgH1-like is a nuclear protein associated with chromatin and other histones. Curiously, TgH1-like is also in the nucleolus and associated with ribosomal proteins, indicating a versatile function in this parasite. Although knockout of the tgh1-like gene does not affect the cell cycle, it causes endopolygeny and asynchronous division. Interestingly, mutation of posttranslationally modified amino acids results in defects in cell division like those in the Δtgh1-like mutant, showing that these sites are important for protein function. Furthermore, in the bradyzoite stage, this protein is expressed only in dividing parasites, reinforcing its importance in cell division. Indeed, the absence of TgH1-like decreases compaction of peripheral chromatin, confirming its role in the chromatin modulation in T. gondii. IMPORTANCE Histone H1, or linker histone, is an important protein that binds to the nucleosome, aiding chromatin compaction. Here, we characterize for the first time a linker histone in T. gondii, named TgH1-like. It is a small and basic protein that corresponds only to the C-terminal portion of the human H1 but is similar to histone H1 from trypanosomatids and bacteria. TgH1-like is located in the nucleus, interacts with nucleosome histones, and acts in chromatin structure and cell division. Our findings show for the first time the presence of a histone H1 protein in an apicomplexan parasite and will provide new insights into cell division and chromatin dynamics in T. gondii and related parasites.

Dataset Information

Cell division in higher plants: a cdc2 gene, its 34-kDa product, and histone H1 kinase activity in pea.

Publications

Cell division in higher plants: a cdc2 gene, its 34-kDa product, and histone H1 kinase activity in pea.

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