<i>Drosophila</i> Orc6 Facilitates GTPase Activity and Filament Formation of the Septin Complex

Huijbregts, Richard P. H.; Svitin, Anton; Stinnett, Monica W.; Renfrow, Matthew B.; Chesnokov, Igor

doi:10.1091/mbc.e08-07-0754

Cited by 46 publications

(89 citation statements)

References 48 publications

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“…The fact that inactivation of the Orc6 NLS prevents both nuclear localization of Orc6 and cell proliferation demonstrates that nuclear localization of Orc6 is essential to Orc6 function. In the absence of Orc6 function, cells accumulated both in G 1 and in G 2 or M phase, consistent with previous reports that siRNA suppression of either human or Drosophila Orc6 expression retards both DNA replication and cytokinesis (27,28).…”

Section: Nuclear Localization Of Orc6-humansupporting

confidence: 92%

Assembly of the Human Origin Recognition Complex Occurs through Independent Nuclear Localization of Its Components

Ghosh

Vassilev

Zhang

et al. 2011

Journal of Biological Chemistry

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Initiation of eukaryotic genome duplication begins when a six-subunit origin recognition complex (ORC) binds to DNA. However, the mechanism by which this occurs in vivo and the roles played by individual subunits appear to differ significantly among organisms. Previous studies identified a soluble human ORC(2-5) complex in the nucleus, an ORC(1-5) complex bound to chromatin, and an Orc6 protein that binds weakly, if at all, to other ORC subunits. Here we show that stable ORC(1-6) complexes also can be purified from human cell extracts and that Orc6 and Orc1 each contain a single nuclear localization signal that is essential for nuclear localization but not for ORC assembly. The Orc6 nuclear localization signal, which is essential for Orc6 function, is facilitated by phosphorylation at its cyclin-dependent kinase consensus site and by association with Kpna6/1, nuclear transport proteins that did not co-purify with other ORC subunits. These and other results support a model in which Orc6, Orc1, and ORC(2-5) are transported independently to the nucleus where they can either assemble into ORC(1-6) or function individually.

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Section: Nuclear Localization Of Orc6-humansupporting

confidence: 92%

Assembly of the Human Origin Recognition Complex Occurs through Independent Nuclear Localization of Its Components

Ghosh

Vassilev

Zhang

et al. 2011

Journal of Biological Chemistry

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“…The larger, N-terminal domain is important for replication, whereas the smaller, C-terminal domain is required for the interaction with Pnut protein and cytokinesis function of Orc6, as demonstrated by our earlier in vitro and cell culture-based studies (18,23). To learn more about the functions of the C-terminal domain in vivo, we designed GFP-Orc6 transgenes containing C-terminal deletions or point mutations and used them in rescue experiments.…”

Section: Generation Of An Orc6 Mutation In Drosophilamentioning

confidence: 99%

“…This apparent inconsistency may reflect the difference in affinity of Orc6 for the core ORC1-5 complex in distant metazoan species. Drosophila Orc6 and human Orc6 also have a function in cytokinesis (7,22,23). This function in Drosophila is attributed to the C-terminal domain of Orc6 (22).…”

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confidence: 99%

Functional analysis of an Orc6 mutant in Drosophila

Balasov

Huijbregts

Chesnokov

2009

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

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The origin recognition complex (ORC) is a 6-subunit complex required for the initiation of DNA replication in eukaryotic organisms. ORC is also involved in other cell functions. The smallest Drosophila ORC subunit, Orc6, is important for both DNA replication and cytokinesis. To study the role of Orc6 in vivo, the orc6 gene was deleted by imprecise excision of P element. Lethal alleles of orc6 are defective in DNA replication and also show abnormal chromosome condensation and segregation. The analysis of cells containing the orc6 deletion revealed that they arrest in both the G 1 and mitotic stages of the cell cycle. Orc6 deletion can be rescued to viability by a full-length Orc6 transgene. The expression of mutant transgenes of Orc6 with deleted or mutated C-terminal domain results in a release of mutant cells from G 1 arrest and restoration of DNA replication, indicating that the DNA replication function of Orc6 is associated with its N-terminal domain. However, these mutant cells accumulate at mitosis, suggesting that the C-terminal domain of Orc6 is important for the passage through the M phase. In a cross-species complementation experiment, the expression of human Orc6 in Drosophila Orc6 mutant cells rescued DNA replication, suggesting that this function of the protein is conserved among metazoans.DNA replication ͉ ORC ͉ Chromatin T he hexameric origin recognition complex (ORC) is an essential component for eukaryotic DNA replication. It was originally discovered in Saccharomyces cerevisiae, and subsequent studies both in yeast and in higher eukaryotes laid the foundation for understanding the functions of this important key initiation factor. ORC binds to origin sites in an ATP-dependent manner and directs the assembly of the prereplicative complex (pre-RC) at the origins (1, 2). ORC subunits and/or complete ORC complexes have also been identified in many metazoan species (1, 3), suggesting the existence of common mechanisms for the initiation of DNA replication in all eukaryotes. ORC genes are essential for cell survival. Mutational analysis of ORC-related genes in yeast and in higher eukaryotes reveals defects in DNA replication (reviewed in refs.

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“…The conservative N-terminal domain is responsible for DNA interaction, and in metazoans shows structural homology with the transcription factor TFIIB [100]. A small variable domain at the C-terminus is responsible for interactions with other proteins, and with ORC3, in particular [20,101,102]. Besides that, it was demonstrated that the C-terminal domain contains a motif which mediates an ORC6 interaction with the Pnut protein, a component of the septin complex [20].…”

Section: Centrosome Duplication and Cytokinesismentioning

confidence: 99%

“…Besides that, it was demonstrated that the C-terminal domain contains a motif which mediates an ORC6 interaction with the Pnut protein, a component of the septin complex [20]. ORC6 promotes septin polymerization due to its ability to form a dimer [102,103]. Although the molecular mechanism for the septin filament assembly still remains poorly understood, the results obtained so far provide strong evidence for the direct involvement of ORC6 in this process.…”

Section: Centrosome Duplication and Cytokinesismentioning

confidence: 99%

Nonreplicative functions of the origin recognition complex

Popova

Brechalov

Георгиева

et al. 2018

Nucleus

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Origin recognition complex (ORC), a heteromeric six-subunit complex, is the central component of the eukaryotic pre-replication complex. Recent data from yeast, frogs, flies and mammals present compelling evidence that ORC and its individual subunits have nonreplicative functions as well. The majority of these functions, such as heterochromatin formation, chromosome condensation, and segregation are dependent on ORC-DNA interactions. Furthermore, ORC is involved in the control of cell division via its participation in centrosome duplication and cytokinesis. Recent findings have also demonstrated a direct interaction between ORC and mRNPs and highlighted an essential role of ORC in mRNA nuclear export. Along with the growth of evolutionary complexity of organisms, ORC complex functions become more elaborate and new functions of the ORC sub-complexes and individual subunits have emerged.

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Drosophila Orc6 Facilitates GTPase Activity and Filament Formation of the Septin Complex

Cited by 46 publications

References 48 publications

Assembly of the Human Origin Recognition Complex Occurs through Independent Nuclear Localization of Its Components

Assembly of the Human Origin Recognition Complex Occurs through Independent Nuclear Localization of Its Components

Functional analysis of an Orc6 mutant in Drosophila

Nonreplicative functions of the origin recognition complex

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