Cloning and characterization of a divergent α-tubulin that is expressed specifically in dividing amebae of Naegleria gruberi

Chung, Sunglan; Cho, Jae-Young; Cheon, HyeonJoo; Paik, Soon-Young; Lee, Joohun

doi:10.1016/s0378-1119(02)00509-7

Cited by 25 publications

(26 citation statements)

References 13 publications

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“…TUBA6), . Interestingly, alpha 6 tubulin has been found in the mitotic spindle‐fiber but is absent in cytoskeletal microtubules in Naegleria gruberi . Our results indicate that depletion of Rab24 causes alterations in the symmetry and the aspect of the spindle during metaphase.…”

Section: Discussionmentioning

confidence: 63%

Rab24 is Required for Normal Cell Division

Militello

Munafó

Berón

et al. 2013

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Rab24 is an atypical member of the Rab GTPase family whose distribution in interphase cells has been characterized; however, its function remains largely unknown. In this study, we have analyzed the distribution of Rab24 throughout cell division. We have observed that Rab24 was located at the mitotic spindle in metaphase, at the midbody during telophase and in the furrow during cytokinesis. We have also observed partial colocalization of Rab24 and tubulin and demonstrated its association to microtubules. Interestingly, more than 90% of transiently transfected HeLa cells with Rab24 presented abnormal nuclear connections (i. e. chromatin bridges). Furthermore, in CHO cells stably transfected with GFP-Rab24wt, we observed a large percentage of binucleated and multinucleated cells. In addition, these cells presented an extremely large size and multiple failures in mitosis, as aberrant spindle formation (metaphase), delayed chromosomes (telophase) and multiple cytokinesis. A marked increase in binucleated, multinucleated and multilobulated nucleus formation was observed in HeLa cells depleted of Rab24. We also present evidence that a fraction of Rab24 associates with microtubules. In addition, Rab24 knock down resulted in misalignment of chromosomes and abnormal spindle formation in metaphase leading to the appearance of delayed chromosomes during late telophase and failures in cytokinesis. Our findings suggest that an adequate level of Rab24 is necessary for normal cell division. In summary, Rab24 modulates several mitotic events, including chromosome segregation and cytokinesis, perhaps through the interaction with microtubules.

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Section: Discussionmentioning

confidence: 63%

Rab24 is Required for Normal Cell Division

Militello

Munafó

Berón

et al. 2013

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“…In addition, BN46/51 was not seen associated with the cytoplasmic microtubules, which are only present in flagellates [16]. The recent description of a mitosis specific form of α-tubulin [17] leaves open the possibility of a specific interaction between spindle microtubules and one or more nucleolar proteins. This possibility remains to be tested.…”

Section: Resultsmentioning

confidence: 99%

The Structure of the Mitotic Spindle and Nucleolus during Mitosis in the Amebo-Flagellate Naegleria

Walsh

2012

PLoS ONE

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Mitosis in the amebo-flagellate Naegleria pringsheimi is acentrosomal and closed (the nuclear membrane does not break down). The large central nucleolus, which occupies about 20% of the nuclear volume, persists throughout the cell cycle. At mitosis, the nucleolus divides and moves to the poles in association with the chromosomes. The structure of the mitotic spindle and its relationship to the nucleolus are unknown. To identify the origin and structure of the mitotic spindle, its relationship to the nucleolus and to further understand the influence of persistent nucleoli on cellular division in acentriolar organisms like Naegleria, three-dimensional reconstructions of the mitotic spindle and nucleolus were carried out using confocal microscopy. Monoclonal antibodies against three different nucleolar regions and α-tubulin were used to image the nucleolus and mitotic spindle. Microtubules were restricted to the nucleolus beginning with the earliest prophase spindle microtubules. Early spindle microtubules were seen as short rods on the surface of the nucleolus. Elongation of the spindle microtubules resulted in a rough cage of microtubules surrounding the nucleolus. At metaphase, the mitotic spindle formed a broad band completely embedded within the nucleolus. The nucleolus separated into two discreet masses connected by a dense band of microtubules as the spindle elongated. At telophase, the distal ends of the mitotic spindle were still completely embedded within the daughter nucleoli. Pixel by pixel comparison of tubulin and nucleolar protein fluorescence showed 70% or more of tubulin co-localized with nucleolar proteins by early prophase. These observations suggest a model in which specific nucleolar binding sites for microtubules allow mitotic spindle formation and attachment. The fact that a significant mass of nucleolar material precedes the chromosomes as the mitotic spindle elongates suggests that spindle elongation drives nucleolar division.

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“…The alpha and beta tubulin clades also include tubulins distinct from those in other eukaryotes. In particular, one clade contains a divergent alpha-tubulin provocatively suggested to be mitosis-specific (Chung et al, 2002). The nature and role of the multiple tubulins are ripe for further study in Naegleria .…”

Section: Naegleria Uses An Unusual Mitotic Spindle Likely Made Of mentioning

confidence: 99%

The Naegleria genome: a free-living microbial eukaryote lends unique insights into core eukaryotic cell biology

Fritz‐Laylin¹,

Ginger

Walsh

et al. 2011

Research in Microbiology

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Naegleria gruberi, a free-living protist, has long been treasured as a model for basal body and flagellar assembly due to its ability to differentiate from crawling amoebae into swimming flagellates. The full genome sequence of Naegleria gruberi has recently been used to estimate gene families ancestral to all eukaryotes and to identify novel aspects of Naegleria biology, including likely facultative anaerobic metabolism, extensive signaling cascades, and evidence for sexuality. Distinctive features of the Naegleria genome and nuclear biology provide unique perspectives for comparative cell biology, including cell division, RNA processing and nucleolar assembly. We highlight here exciting new and novel aspects of Naegleria biology identified through genomic analysis.

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Cloning and characterization of a divergent α-tubulin that is expressed specifically in dividing amebae of Naegleria gruberi

Cited by 25 publications

References 13 publications

Rab24 is Required for Normal Cell Division

Rab24 is Required for Normal Cell Division

The Structure of the Mitotic Spindle and Nucleolus during Mitosis in the Amebo-Flagellate Naegleria

The Naegleria genome: a free-living microbial eukaryote lends unique insights into core eukaryotic cell biology

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