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Tunicate cytostatic factor TC14-3 induces a polycomb group gene and histone modification through Ca(2+) binding and protein dimerization.

Kawamura K, Takakura K, Mori D, Ikeda K, Nakamura A, Suzuki T - BMC Cell Biol. (2012)

Bottom Line: When Phe(65) of TC14-3 was mutated to an acidic amino acid, the resultant mutant protein failed to dimerize.PmEed knockdown by RNA interference rescued cultured cells from the growth-inhibitory effects of TC14-3.These results show that in P. misakiensis, the cytostatic activity of TC14-3 is mediated by PmEed and resultant histone modification, and that the gene expression requires both the protein dimerization and Ca(2+)-binding of TC14-3.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory of Cellular and Molecular Biotechnology, Faculty of Science, Kochi University, Kochi 780-8520, Japan. kazuk@kochi-u.ac.jp

ABSTRACT

Background: As many invertebrate species have multipotent cells that undergo cell growth and differentiation during regeneration and budding, many unique and interesting homeostatic factors are expected to exist in those animals. However, our understanding of such factors and global mechanisms remains very poor. Single zooids of the tunicate, Polyandrocarpa misakiensis, can give off as many as 40 buds during the life span. Bud development proceeds by means of transdifferentiation of very limited number of cells and tissues. TC14-3 is one of several different but closely related polypeptides isolated from P. misakiensis. It acts as a cytostatic factor that regulates proliferation, adhesion, and differentiation of multipotent cells, although the molecular mechanism remains uncertain. The Polycomb group (PcG) genes are involved in epigenetic control of genomic activity in mammals. In invertebrates except Drosophila, PcG and histone methylation have not been studied so extensively, and genome-wide gene regulation is poorly understood.

Results: When Phe(65) of TC14-3 was mutated to an acidic amino acid, the resultant mutant protein failed to dimerize. The replacement of Thr(69) with Arg(69) made dimers unstable. When Glu(106) was changed to Gly(106), the resultant mutant protein completely lost Ca(2+) binding. All these mutant proteins lacked cytostatic activity, indicating the requirement of protein dimerization and calcium for the activity. Polyandrocarpa Eed, a component of PcG, is highly expressed during budding, like TC14-3. When wild-type and mutant TC14-3s were applied in vivo and in vitro to Polyandrocarpa cells, only wild-type TC14-3 could induce Eed without affecting histone methyltransferase gene expression. Eed-expressing cells underwent trimethylation of histone H3 lysine27. PmEed knockdown by RNA interference rescued cultured cells from the growth-inhibitory effects of TC14-3.

Conclusion: These results show that in P. misakiensis, the cytostatic activity of TC14-3 is mediated by PmEed and resultant histone modification, and that the gene expression requires both the protein dimerization and Ca(2+)-binding of TC14-3. This system consisting of a humoral factor, PcG, and histone methylation would contribute to the homeostatic regulation of cell growth and terminal differentiation of invertebrate multipotent cells.

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Calcium-binding kinetics of wild-type and mutant TC14s. (A)Wild type TC14-2 and TC14-3. Note that the Ca2+-binding affinity of TC14-3 is lower than that of TC14-2. (B)TC14-3E106G, TC14-3N109G, and TC14-3K113S.N114E. TC14-3N109G showed lower Ca2+-binding affinity than wild-type TC14-3 and TC14-3K113S.N114G showed the higher affinity to some extent.
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Figure 5: Calcium-binding kinetics of wild-type and mutant TC14s. (A)Wild type TC14-2 and TC14-3. Note that the Ca2+-binding affinity of TC14-3 is lower than that of TC14-2. (B)TC14-3E106G, TC14-3N109G, and TC14-3K113S.N114E. TC14-3N109G showed lower Ca2+-binding affinity than wild-type TC14-3 and TC14-3K113S.N114G showed the higher affinity to some extent.

Mentions: Figure 5 shows the quantitative data of Ca2+ binding in wild-type and mutant TC14s. Wild-type TC14-2 bound to calcium at a molar ratio of 1:0.85, while the calcium binding ratio of wild-type TC14-3 was unexpectedly low (1:0.5) (Figure 5A). TC14-3E106G exhibited negligible Ca2+-binding activity (Figure 5B), and TC14-3N109G exhibited reduced calcium-binding efficiency (molar ratio, 0.4) (Figure 5B). As mentioned, TC14-3E106G lost the cytostatic activity near-completely, while TC14-3N109G exhibited weak cell growth inhibition.


Tunicate cytostatic factor TC14-3 induces a polycomb group gene and histone modification through Ca(2+) binding and protein dimerization.

Kawamura K, Takakura K, Mori D, Ikeda K, Nakamura A, Suzuki T - BMC Cell Biol. (2012)

Calcium-binding kinetics of wild-type and mutant TC14s. (A)Wild type TC14-2 and TC14-3. Note that the Ca2+-binding affinity of TC14-3 is lower than that of TC14-2. (B)TC14-3E106G, TC14-3N109G, and TC14-3K113S.N114E. TC14-3N109G showed lower Ca2+-binding affinity than wild-type TC14-3 and TC14-3K113S.N114G showed the higher affinity to some extent.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3293724&req=5

Figure 5: Calcium-binding kinetics of wild-type and mutant TC14s. (A)Wild type TC14-2 and TC14-3. Note that the Ca2+-binding affinity of TC14-3 is lower than that of TC14-2. (B)TC14-3E106G, TC14-3N109G, and TC14-3K113S.N114E. TC14-3N109G showed lower Ca2+-binding affinity than wild-type TC14-3 and TC14-3K113S.N114G showed the higher affinity to some extent.
Mentions: Figure 5 shows the quantitative data of Ca2+ binding in wild-type and mutant TC14s. Wild-type TC14-2 bound to calcium at a molar ratio of 1:0.85, while the calcium binding ratio of wild-type TC14-3 was unexpectedly low (1:0.5) (Figure 5A). TC14-3E106G exhibited negligible Ca2+-binding activity (Figure 5B), and TC14-3N109G exhibited reduced calcium-binding efficiency (molar ratio, 0.4) (Figure 5B). As mentioned, TC14-3E106G lost the cytostatic activity near-completely, while TC14-3N109G exhibited weak cell growth inhibition.

Bottom Line: When Phe(65) of TC14-3 was mutated to an acidic amino acid, the resultant mutant protein failed to dimerize.PmEed knockdown by RNA interference rescued cultured cells from the growth-inhibitory effects of TC14-3.These results show that in P. misakiensis, the cytostatic activity of TC14-3 is mediated by PmEed and resultant histone modification, and that the gene expression requires both the protein dimerization and Ca(2+)-binding of TC14-3.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory of Cellular and Molecular Biotechnology, Faculty of Science, Kochi University, Kochi 780-8520, Japan. kazuk@kochi-u.ac.jp

ABSTRACT

Background: As many invertebrate species have multipotent cells that undergo cell growth and differentiation during regeneration and budding, many unique and interesting homeostatic factors are expected to exist in those animals. However, our understanding of such factors and global mechanisms remains very poor. Single zooids of the tunicate, Polyandrocarpa misakiensis, can give off as many as 40 buds during the life span. Bud development proceeds by means of transdifferentiation of very limited number of cells and tissues. TC14-3 is one of several different but closely related polypeptides isolated from P. misakiensis. It acts as a cytostatic factor that regulates proliferation, adhesion, and differentiation of multipotent cells, although the molecular mechanism remains uncertain. The Polycomb group (PcG) genes are involved in epigenetic control of genomic activity in mammals. In invertebrates except Drosophila, PcG and histone methylation have not been studied so extensively, and genome-wide gene regulation is poorly understood.

Results: When Phe(65) of TC14-3 was mutated to an acidic amino acid, the resultant mutant protein failed to dimerize. The replacement of Thr(69) with Arg(69) made dimers unstable. When Glu(106) was changed to Gly(106), the resultant mutant protein completely lost Ca(2+) binding. All these mutant proteins lacked cytostatic activity, indicating the requirement of protein dimerization and calcium for the activity. Polyandrocarpa Eed, a component of PcG, is highly expressed during budding, like TC14-3. When wild-type and mutant TC14-3s were applied in vivo and in vitro to Polyandrocarpa cells, only wild-type TC14-3 could induce Eed without affecting histone methyltransferase gene expression. Eed-expressing cells underwent trimethylation of histone H3 lysine27. PmEed knockdown by RNA interference rescued cultured cells from the growth-inhibitory effects of TC14-3.

Conclusion: These results show that in P. misakiensis, the cytostatic activity of TC14-3 is mediated by PmEed and resultant histone modification, and that the gene expression requires both the protein dimerization and Ca(2+)-binding of TC14-3. This system consisting of a humoral factor, PcG, and histone methylation would contribute to the homeostatic regulation of cell growth and terminal differentiation of invertebrate multipotent cells.

Show MeSH
Related in: MedlinePlus