Actin and tubulin in <i>Tetrahymena</i>

Mitchell, E J; Zimmerman, Selma; Zimmerman, Arthur M.

doi:10.1139/o85-058

Cited by 8 publications

(6 citation statements)

References 3 publications

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“…Maximum expression of THD2 occurred at 80 and 200 min, which were the times when the greatest numbers of cells were in micronuclear mitosis. The expression of ACT1, which does not change throughout the cell cycle, was monitored as a control (34,62). Since micronuclear DNA synthesis occurs immediately following anaphase, the observed peak of THD2 expression coincident with anaphase was consistent with the possibility that Thd2a might deacetylate newly deposited histones.…”

Section: Resultsmentioning

confidence: 94%

A Class II Histone Deacetylase Acts on Newly Synthesized Histones in Tetrahymena

et al. 2008

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Newly synthesized histones are acetylated prior to their deposition into nucleosomes. Following nucleosome formation and positioning, they are rapidly deacetylated, an event that coincides with further maturation of the chromatin fiber. The histone deacetylases (HDACs) used for histone deposition and de novo chromatin formation are poorly understood. In the ciliate Tetrahymena thermophila, transcription-related deacetylation in the macronucleus is physically separated from deposition-related deacetylation in the micronucleus. This feature was utilized to identify an HDAC named Thd2, a class II HDAC that acts on newly synthesized histones to remove deposition-related acetyl moieties. The THD2 transcript is alternatively spliced, and the major form contains a putative inositol polyphosphate kinase (IPK) domain similar to Ipk2, an enzyme that promotes chromatin remodeling by SWI/SNF remodeling complexes. Cells lacking Thd2, which retain deposition-related acetyl moieties on new histones, exhibit chromatin and cytological phenotypes indicative of a role for Thd2 in chromatin maturation, including the proteolytic processing of histone H3.

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Section: Resultsmentioning

confidence: 94%

A Class II Histone Deacetylase Acts on Newly Synthesized Histones in Tetrahymena

et al. 2008

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“…The (30) reported that a 47.5-kDa protein, which they considered to be actin, was partially purified from Tetrahymena cells by using a DNase I affinity column. Our results indicate that Tetrahymena actin does not inhibit DNase I activity at all.…”

Section: Resultsmentioning

confidence: 99%

“…Actin is ubiquitous in eukaryotes, but its existence has not been undisputably proven in Tetrahymena despite many attempts (1). Recently, the actin genes from Tetrahymena thermophila and Tetrahymena pyriformis were isolated, respectively, by Cupples and Pearlman (2) and by ourselves (3).…”

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confidence: 99%

Purification of Tetrahymena actin reveals some unusual properties.

Hirono

Kumagai

Numata

et al. 1989

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

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Actin from Tetrahymena pyriformis has been purified by monitoring the presence of the actin gene product with an antiserum against a synthetic N-terminal peptide deduced from the nucleotide sequence of the Tetrahymena actin gene that we cloned previously. This highly purified Tetrahymena actin shares many essential properties with ubiquitous actin, including ion-dependent polymerization to microfilaments, binding with muscle heavy meromyosin to form arrowheads, and activation of the Mg2+-ATPase of muscle myosin subfragment 1. On the other hand, some properties of this purified Tetrahymena actin dearly differ from those of muscle actin: (i) Tetrahymena actin has 8 times less ability to activate the Mg2I-ATPase of muscle myosin subfragment 1 than muscle actin; (ii) Tetrahymena actin did not bind to phalloidin at all; (iii) Tetrahymena actin did not inhibit DNase I activity at all. In general, Tetrahymena actin has very unusual properties when compared to other actins described so far. This actin is expected to provide important clues for elucidating problems concerning the relationships between the structural and functional domains in an actin molecule.

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“…The presence of LdACT in the construct was examined by restriction enzyme digestion and the nucleotide sequence was confirmed by DNA sequencing using the dideoxy chain termination method (25). 40 g of both the p6.5-LdACT construct and p6.5 control plasmids were transfected separately into 10 7 L. donovani promastigotes by electroporation (26). Transfected cells were further selected in the growth medium containing tunicamycin up to 20 g/ml and maintained in the same conditions.…”

Section: Plasmid Construction Transfection and Expressionmentioning

confidence: 99%

An Unconventional Form of Actin in Protozoan Hemoflagellate, Leishmania

Kapoor

Sahasrabuddhe

Kumar

et al. 2008

Journal of Biological Chemistry

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Leishmania actin was cloned, overexpressed in baculovirusinsect cell system, and purified to homogeneity. The purified protein polymerized optimally in the presence of Mg 2؉ and ATP, but differed from conventional actins in its following properties: (i) it did not polymerize in the presence of Mg 2؉ alone, (ii) it polymerized in a restricted range of pH 7.0 -8.5, (iii) its critical concentration for polymerization was found to be 3-4-fold lower than of muscle actin, (iv) it predominantly formed bundles rather than single filaments at pH 8.0, (v) it displayed considerably higher ATPase activity during polymerization, (vi) it did not inhibit DNase-I activity, and (vii) it did not bind the F-actin-binding toxin phalloidin or the actin polymerization disrupting agent Latrunculin B. Computational and molecular modeling studies revealed that the observed unconventional behavior of Leishmania actin is related to the diverged amino acid stretches in its sequence, which may lead to changes in the overall charge distribution on its solvent-exposed surface, ATP binding cleft, Mg 2؉ binding sites, and the hydrophobic loop that is involved in monomer-monomer interactions. Phylogenetically, it is related to ciliate actins, but to the best of our knowledge, no other actin with such unconventional properties has been reported to date. It is therefore suggested that actin in Leishmania may serve as a novel target for design of new antileishmanial drugs.

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Actin and tubulin in Tetrahymena

Cited by 8 publications

References 3 publications

A Class II Histone Deacetylase Acts on Newly Synthesized Histones in Tetrahymena

A Class II Histone Deacetylase Acts on Newly Synthesized Histones in Tetrahymena

Purification of Tetrahymena actin reveals some unusual properties.

An Unconventional Form of Actin in Protozoan Hemoflagellate, Leishmania

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