The cell cycle-dependent localization of the CP190 centrosomal protein is determined by the coordinate action of two separable domains.

CP190, a protein of 1,096 amino acids from Drosophila melanogaster, oscillates in a cell cycle-specific manner between the nucleus during interphase, and the centrosome during mitosis. To characterize the regions of CP190 responsible for its dynamic behavior, we injected rhodamine-labeled fusion proteins spanning most of CP190 into early Drosophila embryos, where their localizations were characterized using time-lapse fluorescence confocal microscopy. A single bipartite 19-amino acid nuclear localization signal was detected that causes nuclear localization. Robust centrosomal localization is conferred by a separate region of 124 amino acids; two adjacent, nonoverlapping fusion proteins containing distinct portions of this region show weaker centrosomal localization. Fusion proteins that contain both nuclear and centrosomal localization sequences oscillate between the nucleus and the centrosome in a manner identical to native CP190. Fusion proteins containing only the centrosome localization sequence are found at centrosomes throughout the cell cycle, suggesting that CP190 is actively recruited away from the centrosome by its movement into the nucleus during interphase. Both native and bacterially expressed CP190 cosediment with microtubules in vitro. Tests with fusion proteins show that the domain responsible for microtubule binding overlaps the domain required for centrosomal localization. CP60, a protein identified by its association with CP190, also localizes to centrosomes and to nuclei in a cell cycle-dependent manner. Experiments in which colchicine is used to depolymerize microtubules in the early Drosophila embryo demonstrate that both CP190 and CP60 are able to attain and maintain their centrosomal localization in the absence of microtubules.

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PTOV1 Enables the Nuclear Translocation and Mitogenic Activity of Flotillin-1, a Major Protein of Lipid Rafts

Molecular and Cellular Biology ◽

10.1128/mcb.25.5.1900-1911.2005 ◽

2005 ◽

Vol 25 (5) ◽

pp. 1900-1911 ◽

Cited By ~ 66

Author(s):

Anna Santamaría ◽

Elisabeth Castellanos ◽

Valentí Gómez ◽

Patricia Benedit ◽

Jaime Renau-Piqueras ◽

...

Keyword(s):

Cell Cycle ◽

Cell Proliferation ◽

Nuclear Localization ◽

Nuclear Translocation ◽

Subcellular Fractionation ◽

Major Protein ◽

Dependent Manner ◽

Protein Levels ◽

A Cell ◽

Cycle Dependent

ABSTRACT PTOV1 is a mitogenic protein that shuttles between the nucleus and the cytoplasm in a cell cycle-dependent manner. It consists of two homologous domains arranged in tandem that constitute a new class of protein modules. We show here that PTOV1 interacts with the lipid raft protein flotillin-1, with which it copurifies in detergent-insoluble floating fractions. Flotillin-1 colocalized with PTOV1 not only at the plasma membrane but, unexpectedly, also in the nucleus, as demonstrated by immunocytochemistry and subcellular fractionation of endogenous and exogenous flotillin-1. Flotillin-1 entered the nucleus concomitant with PTOV1, shortly before the initiation of the S phase. Protein levels of PTOV1 and flotillin-1 oscillated during the cell cycle, with a peak in S. Depletion of PTOV1 significantly inhibited nuclear localization of flotillin-1, whereas depletion of flotillin-1 did not affect nuclear localization of PTOV1. Depletion of either protein markedly inhibited cell proliferation under basal conditions. Overexpression of PTOV1 or flotillin-1 strongly induced proliferation, which required their localization to the nucleus, and was dependent on the reciprocal protein. These observations suggest that PTOV1 assists flotillin-1 in its translocation to the nucleus and that both proteins are required for cell proliferation.

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Truncated APC regulates the transcriptional activity of β-catenin in a cell cycle dependent manner

Human Molecular Genetics ◽

10.1093/hmg/ddl464 ◽

2006 ◽

Vol 16 (2) ◽

pp. 199-209 ◽

Cited By ~ 38

Author(s):

Jean Schneikert ◽

Annette Grohmann ◽

Jürgen Behrens

Keyword(s):

Cell Cycle ◽

Transcriptional Activity ◽

Dependent Manner ◽

A Cell ◽

Cycle Dependent

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E2F activity is regulated by cell cycle-dependent changes in subcellular localization.

Molecular and Cellular Biology ◽

10.1128/mcb.17.12.7268 ◽

1997 ◽

Vol 17 (12) ◽

pp. 7268-7282 ◽

Cited By ~ 142

Author(s):

R Verona ◽

K Moberg ◽

S Estes ◽

M Starz ◽

J P Vernon ◽

...

Keyword(s):

Cell Cycle ◽

Subcellular Localization ◽

Nuclear Localization ◽

Mammalian Cells ◽

Critical Role ◽

Biological Properties ◽

Dependent Manner ◽

Restriction Point ◽

Cycle Dependent ◽

Almost All

E2F directs the cell cycle-dependent expression of genes that induce or regulate the cell division process. In mammalian cells, this transcriptional activity arises from the combined properties of multiple E2F-DP heterodimers. In this study, we show that the transcriptional potential of individual E2F species is dependent upon their nuclear localization. This is a constitutive property of E2F-1, -2, and -3, whereas the nuclear localization of E2F-4 is dependent upon its association with other nuclear factors. We previously showed that E2F-4 accounts for the majority of endogenous E2F species. We now show that the subcellular localization of E2F-4 is regulated in a cell cycle-dependent manner that results in the differential compartmentalization of the various E2F complexes. Consequently, in cycling cells, the majority of the p107-E2F, p130-E2F, and free E2F complexes remain in the cytoplasm. In contrast, almost all of the nuclear E2F activity is generated by pRB-E2F. This complex is present at high levels during G1 but disappears once the cells have passed the restriction point. Surprisingly, dissociation of this complex causes little increase in the levels of nuclear free E2F activity. This observation suggests that the repressive properties of the pRB-E2F complex play a critical role in establishing the temporal regulation of E2F-responsive genes. How the differential subcellular localization of pRB, p107, and p130 contributes to their different biological properties is also discussed.

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Ser68 phosphoregulation is essential for CENP-A deposition, centromere function and viability in mice

10.1101/2021.11.23.469796 ◽

2021 ◽

Author(s):

Yuting Liu ◽

Kehui Wang ◽

Li Huang ◽

Jicheng Zhao ◽

Xinpeng Chen ◽

...

Keyword(s):

Cell Cycle ◽

Cell Viability ◽

Histone H3 ◽

Dependent Manner ◽

Centromere Function ◽

Histone H3 Variant ◽

A Cell ◽

Cycle Dependent ◽

Spatiotemporal Control

Centromere identity is defined by nucleosomes containing CENP-A, a histone H3 variant. The deposition of CENP-A at centromeres is tightly regulated in a cell-cycle-dependent manner. We previously reported that the spatiotemporal control of centromeric CENP-A incorporation is mediated by the phosphorylation of CENP-A Ser68. However, a recent report argued that Ser68 phosphoregulation is dispensable for accurate CENP-A loading. Here, we report that the substitution of Ser68 of endogenous CENP-A with either Gln68 or Glu68 severely impairs CENP-A deposition and cell viability. We also find that mice harboring the corresponding mutations are lethal. Together, these results indicate that the dynamic phosphorylation of Ser68 ensures cell-cycle-dependent CENP-A deposition and cell viability.

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Gcn5-mediated acetylation at MBF-regulated promoters induces the G1/S transcriptional wave

Nucleic Acids Research ◽

10.1093/nar/gkz561 ◽

2019 ◽

Vol 47 (16) ◽

pp. 8439-8451 ◽

Cited By ~ 1

Author(s):

Alberto González-Medina ◽

Elena Hidalgo ◽

José Ayté

Keyword(s):

Cell Cycle ◽

Molecular Mechanisms ◽

Histone H3 ◽

Dependent Manner ◽

Saga Complex ◽

Lysine Residues ◽

Physical Barriers ◽

A Cell ◽

Cycle Dependent ◽

Regulated Promoters

Abstract In fission yeast, MBF-dependent transcription is inactivated at the end of S phase through a negative feedback loop that involves the co-repressors, Yox1 and Nrm1. Although this repression system is well known, the molecular mechanisms involved in MBF activation remain largely unknown. Compacted chromatin constitutes a barrier to activators accessing promoters. Here, we show that chromatin regulation plays a key role in activating MBF-dependent transcription. Gcn5, a part of the SAGA complex, binds to MBF-regulated promoters through the MBF co-activator Rep2 in a cell cycle-dependent manner and in a reverse correlation to the binding of the MBF co-repressors, Nrm1 or Yox1. We propose that the co-repressors function as physical barriers to SAGA recruitment onto MBF promoters. We also show that Gcn5 acetylates specific lysine residues on histone H3 in a cell cycle-regulated manner. Furthermore, either in a gcn5 mutant or in a strain in which histone H3 is kept in an unacetylated form, MBF-dependent transcription is downregulated. In summary, Gcn5 is required for the full activation and correct timing of MBF-regulated gene transcription.

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Regulated nuclear import of the Drosophila rel protein dorsal: structure-function analysis.

Molecular and Cellular Biology ◽

10.1128/mcb.16.3.1103 ◽

1996 ◽

Vol 16 (3) ◽

pp. 1103-1114 ◽

Cited By ~ 22

Author(s):

S Govind ◽

E Drier ◽

L H Huang ◽

R Steward

Keyword(s):

Amino Acids ◽

Structure Function ◽

Nuclear Localization ◽

Nuclear Import ◽

Function Analysis ◽

Drosophila Embryo ◽

Nuclear Targeting ◽

Homology Region ◽

Early Drosophila Embryo

The formation of a gradient of nuclear Dorsal protein in the early Drosophila embryo is the last step in a maternally encoded dorsal-ventral signal transduction pathway. This gradient is formed in response to a ventral signal, which leads to the dissociation of cytoplasmic Dorsal from the I kappa B homolog Cactus. Free Dorsal is then targeted to the nucleus. Dorsal is a Rel-family transcription factor. Signal-dependent nuclear localization characterizes the regulation of Rel proteins. In order to identify regions of Dorsal that are essential for its homodimerization, nuclear targeting, and interaction with Cactus, we have performed an in vivo structure-function analysis. Our results show that all these functions are carried out by regions within the conserved Rel-homology region of Dorsal. The C-terminal divergent half of Dorsal is dispensable for its selective nuclear import. A basic stretch of 6 amino acids at the C terminus of the Rel-homology region is necessary for nuclear localization. This nuclear localization signal is not required for Cactus binding. Removal of the N-terminal 40 amino acids abolished the nuclear import of Dorsal, uncovering a potentially novel function for this highly conserved region.

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