Cell Cycle Activation of the Swi6p Transcription Factor Is Linked to Nucleocytoplasmic Shuttling

ABSTRACT The control of the subcellular localization of cell cycle regulators has emerged as a crucial mechanism in the regulation of cell division. In the present work, we have characterized the function of the karyopherin Msn5p in the control of the cell cycle of Saccharomyces cerevisiae. Phenotypic analysis of the msn5 mutant revealed an increase in cell size and a functional interaction between Msn5p and the cell cycle transcription factor SBF (composed of the Swi4p and Swi6p proteins), indicating that Msn5p is involved in Start control. In fact, we have shown that the level of Cln2p protein is drastically reduced in an msn5 mutant. The effect on CLN2 expression is mediated at a transcriptional level, Msn5p being necessary for proper SBF-dependent transcription. On the contrary, loss of MSN5 has no effect on the closely related transcription factor MBF (composed of the Mbp1p and Swi6p proteins). Regulation of SBF by Msn5p is exerted by control of the localization of the regulatory subunit Swi6p. Swi6p shuttles between the nucleus and the cytoplasm during the cell cycle, and we have found that Msn5p is required for Swi6p export from the nucleus during the G2-M phase. What is more important, we have demonstrated that export of Swi6p to the cytoplasm is required for SBF activity, providing evidence for a functional switch of Swi6p linked to its nucleocytoplasmic shuttling during the cell cycle.

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Pivotal Role of Survivin in Leukemogenesis by E2A-HLF Chimeric Transcription Factor.

Blood ◽

10.1182/blood.v106.11.2988.2988 ◽

2005 ◽

Vol 106 (11) ◽

pp. 2988-2988

Author(s):

Mayuko Okuya ◽

Hidemitsu Kurosawa ◽

Takayuki Matsunaga ◽

Mitsuoki Eguchi ◽

Yusuke Furukawa ◽

...

Keyword(s):

Cell Cycle ◽

Transcription Factor ◽

Survivin Expression ◽

Small Population ◽

Dominant Negative ◽

Dominant Negative Mutant ◽

Transcriptional Level ◽

Survivin Promoter ◽

M Phase ◽

Negative Mutant

Abstract The E2A-HLF fusion transcription factor generated by the t(17;19)(q22;p13) translocation is found in a small population of pro-B cell ALL. Patients associated with this chimera share distinct clinical features such as hypercalcemia, coagulopathy and very poor prognosis due to resistance to intensive chemotherapy including aggressive conditioning for BMT, all of which are unusual for this type of ALL. We have previously demonstrated that inhibition of the trans-activation potential of the E2A-HLF chimera by the dominant negative mutant results in apoptosis in t(17;19)+ ALL cells but does not affect cell cycle. Moreover, E2A-HLF blocks apoptosis induced by cytokine deprivation in IL-3-dependent cells, suggesting that this fusion protein contributes to leukemogenesis by substituting for the anti-apoptotic function of cytokines. The present study shows that survivin is a downstream target molecule of E2A-HLF. Four t(17;19)+ ALL cell lines expressed survivin at high levels and down-regulation of E2A-HLF function by the dominant negative mutant suppressed survivin expression. In addition, forced expression of E2A-HLF in Nalm-6, a t(17;19)− ALL cell line, up-regulated survivin expression. Survivin is known to be expressed predominantly in the G2/M phase. Indeed, separation of the fractions enriched for in each phase of the cell cycle using a counterflow centrifugal elutriator revealed G2/M phase-dominant survivin expression in t(17;19) − ALL cells including Nalm-6. In t(17;19)+ ALL cells, however, survivin was expressed throughout the cell cycle. Moreover, Nalm-6 cells forced to express E2A-HLF showed cell cycle-independent survivin expression. Reporter assay revealed that E2A-HLF induced luciferase activity by transfecting with each reporter construct containing the survivin promoter at a different length from the initial ATG, suggesting that E2A-HLF induces survivin expression at the transcriptional level, but not by direct binding of E2A-HLF to the survivin promoter. To test whether survivin plays anti-apoptotic roles in t(17:19)+ cells, we used a survivin mutant lacking a phosphorylation site (T34A-survivin) and considered to inhibit survivin function in a dominant negative manner. T34A-survivin induced massive apoptosis throughout the cell cycle in t(17;19)+ cells. In contrast, T34A-survivin in t(17;19) − cells induced cell death in only a small population in G2/M phase. In addition to caspase-dependent pathways, T34A-survivin induced apoptosis in t(17;19)+ ALL cells through caspase-independent pathways, in which apoptosis-inducing factor (AIF) translocated from cytoplasm to the nucleus. These results indicate that cell cycle-independent up-regulation of survivin by the E2A-HLF chimera is indispensable for the survival of t(17;19)+ ALL cells, and that inhibition of survivin may offer an effective therapeutic strategy against this refractory ALL.

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Transcription factors important for starting the cell cycle in yeast

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.1993.0078 ◽

1993 ◽

Vol 340 (1293) ◽

pp. 351-360 ◽

Cited By ~ 11

Keyword(s):

Cell Cycle ◽

Transcription Factor ◽

Dna Replication ◽

Transcriptional Activation ◽

Feedback Loop ◽

Cell Cycle Progression ◽

Regulatory Subunit ◽

Cycle Progression ◽

Embryonic Cleavage ◽

Related Transcription Factor

Unlike early embryonic cleavage divisions in certain animals, cell-cycle progression in yeast and probably also in all metazoan somatic cells requires the periodic transcriptional activation of certain key genes. Thus far, the only clear examples are genes that encode a class of unstable ‘cyclin’ proteins, which bind and activate the cdc2/Cdc28 protein kinase: the G1-specific cyclins encoded by CLN1 and CLN2 , a B-type cyclin implicated in DNA replication encoded by CLB5 ; and four B-type cyclins involved in mitosis encoded by CLB1, 2, 3, 4. CLN1, CLN2 , and CLB5 are transcribed in late G1, as cells undergo Start. A transcription factor composed of Swi4 and Swi6 proteins (called SBF) activates CLN1 and CLN2 transcription via a positive feedback loop in which Cln proteins activate their own transcription. A different but related transcription factor called MBF seems responsible for the late G1-specific transcription of most DNA replication genes including CLB5 . We have purified MBF and shown that it contains Swi6 and a 110-120 kDa protein distinct from Swi4 (pl20) that contacts DNA. Thus, we propose that SBF and MBF share a common regulatory subunit (Swi6) but recognize their promoter elements via distinct DNA binding subunits.

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SOG1 transcription factor promotes the onset of endoreduplication under salinity stress in Arabidopsis

Scientific Reports ◽

10.1038/s41598-021-91293-1 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Kalyan Mahapatra ◽

Sujit Roy

Keyword(s):

Cell Cycle ◽

Dna Damage ◽

Cell Death ◽

Transcription Factor ◽

Programmed Cell Death ◽

Salinity Stress ◽

Crucial Role ◽

Genome Stability ◽

Cell Cycle Checkpoint ◽

Cell Cycle Regulators

AbstractAs like in mammalian system, the DNA damage responsive cell cycle checkpoint functions play crucial role for maintenance of genome stability in plants through repairing of damages in DNA and induction of programmed cell death or endoreduplication by extensive regulation of progression of cell cycle. ATM and ATR (ATAXIA-TELANGIECTASIA-MUTATED and -RAD3-RELATED) function as sensor kinases and play key role in the transmission of DNA damage signals to the downstream components of cell cycle regulatory network. The plant-specific NAC domain family transcription factor SOG1 (SUPPRESSOR OF GAMMA RESPONSE 1) plays crucial role in transducing signals from both ATM and ATR in presence of double strand breaks (DSBs) in the genome and found to play crucial role in the regulation of key genes involved in cell cycle progression, DNA damage repair, endoreduplication and programmed cell death. Here we report that Arabidopsis exposed to high salinity shows generation of oxidative stress induced DSBs along with the concomitant induction of endoreduplication, displaying increased cell size and DNA ploidy level without any change in chromosome number. These responses were significantly prominent in SOG1 overexpression line than wild-type Arabidopsis, while sog1 mutant lines showed much compromised induction of endoreduplication under salinity stress. We have found that both ATM-SOG1 and ATR-SOG1 pathways are involved in the salinity mediated induction of endoreduplication. SOG1was found to promote G2-M phase arrest in Arabidopsis under salinity stress by downregulating the expression of the key cell cycle regulators, including CDKB1;1, CDKB2;1, and CYCB1;1, while upregulating the expression of WEE1 kinase, CCS52A and E2Fa, which act as important regulators for induction of endoreduplication. Our results suggest that Arabidopsis undergoes endoreduplicative cycle in response to salinity induced DSBs, showcasing an adaptive response in plants under salinity stress.

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Functions of Cyclin A1 in the Cell Cycle and Its Interactions with Transcription Factor E2F-1 and the Rb Family of Proteins

Molecular and Cellular Biology ◽

10.1128/mcb.19.3.2400 ◽

1999 ◽

Vol 19 (3) ◽

pp. 2400-2407 ◽

Cited By ~ 94

Author(s):

Rong Yang ◽

Carsten Müller ◽

Vong Huynh ◽

Yuen K. Fung ◽

Amy S. Yee ◽

...

Keyword(s):

Cell Cycle ◽

Transcription Factor ◽

Mitotic Cell ◽

Histone H1 ◽

Mitotic Cell Cycle ◽

Osteosarcoma Cell ◽

Cell Cycle Regulators ◽

Cyclin A1 ◽

Transcription Factor E2f

ABSTRACT Human cyclin A1, a newly discovered cyclin, is expressed in testis and is thought to function in the meiotic cell cycle. Here, we show that the expression of human cyclin A1 and cyclin A1-associated kinase activities was regulated during the mitotic cell cycle. In the osteosarcoma cell line MG63, cyclin A1 mRNA and protein were present at very low levels in cells at the G0 phase. They increased during the progression of the cell cycle and reached the highest levels in the S and G2/M phases. Furthermore, the cyclin A1-associated histone H1 kinase activity peaked at the G2/M phase. We report that cyclin A1 could bind to important cell cycle regulators: the Rb family of proteins, the transcription factor E2F-1, and the p21 family of proteins. The in vitro interaction of cyclin A1 with E2F-1 was greatly enhanced when cyclin A1 was complexed with CDK2. Associations of cyclin A1 with Rb and E2F-1 were observed in vivo in several cell lines. When cyclin A1 was coexpressed with CDK2 in sf9 insect cells, the CDK2-cyclin A1 complex had kinase activities for histone H1, E2F-1, and the Rb family of proteins. Our results suggest that the Rb family of proteins and E2F-1 may be important targets for phosphorylation by the cyclin A1-associated kinase. Cyclin A1 may function in the mitotic cell cycle in certain cells.

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C/EBPϵ interacts with retinoblastoma and E2F1 during granulopoiesis

Blood ◽

10.1182/blood-2003-01-0159 ◽

2004 ◽

Vol 103 (3) ◽

pp. 828-835 ◽

Cited By ~ 45

Author(s):

Sigal Gery ◽

Adrian F. Gombart ◽

Yuen K. Fung ◽

H. Phillip Koeffler

Keyword(s):

Cell Cycle ◽

Transcription Factor ◽

Broad Spectrum ◽

Transcriptional Activity ◽

Myeloid Cells ◽

Cell Cycle Regulators ◽

Granulocytic Differentiation ◽

Specific Transcription Factor ◽

Enhancer Binding Protein ◽

Reporter Assays

AbstractCCAAT enhancer binding protein epsilon (C/EBPϵ) is a myeloid specific transcription factor that is essential for terminal granulocytic differentiation. Retinoblastoma (Rb) and E2F1 are critical cell cycle regulators that also have been implicated in several differentiation systems. Here, we demonstrate that C/EBPϵ interacts with Rb and E2F1 during granulocytic differentiation in NB4 and U937 human myeloid cells and in 32Dcl3 murine myeloid precursor cells. The interaction between C/EBPϵ and Rb enhances C/EBPϵ-mediated transcription of myeloid specific genes both in reporter assays and endogenously. The C/EBPϵ-E2F1 interaction results in repression of E2F1-mediated transcriptional activity. Finally, overexpression of C/EBPϵ in human myeloid cells leads to down-regulation of c-Myc. We propose that the interactions between C/EBPϵ, a tissue-specific transcription factor, and the broad-spectrum proteins, Rb and E2F1, are important in C/EBPϵ-induced terminal granulocytic differentiation.

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Degradation of the Transcription Factor Gcn4 Requires the Kinase Pho85 and the SCFCDC4 Ubiquitin–Ligase Complex

Molecular Biology of the Cell ◽

10.1091/mbc.11.3.915 ◽

2000 ◽

Vol 11 (3) ◽

pp. 915-927 ◽

Cited By ~ 97

Author(s):

Ariella Meimoun ◽

Tsvi Holtzman ◽

Ziva Weissman ◽

Helen J. McBride ◽

David J. Stillman ◽

...

Keyword(s):

Cell Cycle ◽

Transcription Factor ◽

Ubiquitin Ligase ◽

Protein A ◽

Purine Biosynthesis ◽

Cell Cycle Regulators ◽

Rich Medium ◽

Ubiquitin Ligase Complex ◽

Ubiquitin Conjugating Enzyme ◽

The Stability

Gcn4, a yeast transcriptional activator that promotes the expression of amino acid and purine biosynthesis genes, is rapidly degraded in rich medium. Here we report that SCFCDC4, a recently characterized protein complex that acts in conjunction with the ubiquitin-conjugating enzyme Cdc34 to degrade cell cycle regulators, is also necessary for the degradation of the transcription factor Gcn4. Degradation of Gcn4 occurs throughout the cell cycle, whereas degradation of the known cell cycle substrates of Cdc34/SCFCDC4 is cell cycle regulated. Gcn4 ubiquitination and degradation are regulated by starvation for amino acids, whereas the degradation of the cell cycle substrates of Cdc34/SCFCDC4 is unaffected by starvation. We further show that unlike the cell cycle substrates of Cdc34/SCFCDC4, which require phosphorylation by the kinase Cdc28, Gcn4 degradation requires the kinase Pho85. We identify the critical target site of Pho85 on Gcn4; a mutation of this site stabilizes the protein. A specific Pho85-Pcl complex that is able to phosphorylate Gcn4 on that site is inactive under conditions under which Gcn4 is stable. Thus, Cdc34/SCFCDC4 activity is constitutive, and regulation of the stability of its various substrates occurs at the level of their phosphorylation.

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Subcellular localization of EEN/endophilin A2, a fusion partner gene in leukaemia

Biochemical Journal ◽

10.1042/bj20040041 ◽

2004 ◽

Vol 383 (1) ◽

pp. 27-35 ◽

Cited By ~ 8

Author(s):

Ngai CHEUNG ◽

Chi Wai SO ◽

Judy W. P. YAM ◽

C. K. C. SO ◽

Randy Y. C. POON ◽

...

Keyword(s):

Cell Cycle ◽

Subcellular Localization ◽

Fusion Partner ◽

Nucleocytoplasmic Shuttling ◽

Cellular Functions ◽

Protein Levels ◽

Mixed Lineage Leukaemia ◽

Partner Gene ◽

M Phase ◽

Endocytic Vesicles

EEN (extra eleven nineteen), also known as EA2 (endophilin A2), a fusion partner of the MLL (mixed-lineage leukaemia) gene in human acute leukaemia, is a member of the endophilin A family, involved in the formation of endocytic vesicles. We present evidence to show that EEN/EA2 is localized predominantly in nuclei of various cell lines of haemopoietic, fibroblast and epithelial origin, in contrast with its reported cytoplasmic localization in neurons and osteoclasts, and that EEN/EA2 exhibits nucleocytoplasmic shuttling. During the cell cycle, EEN/EA2 shows dynamic localization: it is perichromosomal in prometaphase, co-localizes with the bipolar spindle in metaphase and anaphase and redistributes to the midzone and midbody in telophase. This pattern of distribution coincides with changes in protein levels of EEN/EA2, with the highest levels being observed in G2/M-phase. Our results suggest that distinct subcellular localization of the endophilin A family members probably underpins their diverse cellular functions and indicates a role for EEN/EA2 in the cell cycle.

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Essential Dosage-Dependent Functions of the Transcription Factor Yin Yang 1 in Late Embryonic Development and Cell Cycle Progression

Molecular and Cellular Biology ◽

10.1128/mcb.26.9.3565-3581.2006 ◽

2006 ◽

Vol 26 (9) ◽

pp. 3565-3581 ◽

Cited By ~ 119

Author(s):

El Bachir Affar ◽

Frédérique Gay ◽

Yujiang Shi ◽

Huifei Liu ◽

Maite Huarte ◽

...

Keyword(s):

Cell Cycle ◽

Cell Proliferation ◽

Transcription Factor ◽

Cell Cycle Progression ◽

Target Genes ◽

Eukaryotic Cell ◽

Dependent Manner ◽

Phenotypic Analysis ◽

Yin Yang 1 ◽

Yin Yang

ABSTRACT Constitutive ablation of the Yin Yang 1 (YY1) transcription factor in mice results in peri-implantation lethality. In this study, we used homologous recombination to generate knockout mice carrying yy1 alleles expressing various amounts of YY1. Phenotypic analysis of yy1 mutant embryos expressing ∼75%, ∼50%, and ∼25% of the normal complement of YY1 identified a dosage-dependent requirement for YY1 during late embryogenesis. Indeed, reduction of YY1 levels impairs embryonic growth and viability in a dose-dependent manner. Analysis of the corresponding mouse embryonic fibroblast cells also revealed a tight correlation between YY1 dosage and cell proliferation, with a complete ablation of YY1 inducing cytokinesis failure and cell cycle arrest. Consistently, RNA interference-mediated inhibition of YY1 in HeLa cells prevents cytokinesis, causes proliferative arrest, and increases cellular sensitivity to various apoptotic agents. Genome-wide expression profiling identified a plethora of YY1 target genes that have been implicated in cell growth, proliferation, cytokinesis, apoptosis, development, and differentiation, suggesting that YY1 coordinates multiple essential biological processes through a complex transcriptional network. These data not only shed new light on the molecular basis for YY1 developmental roles and cellular functions, but also provide insight into the general mechanisms controlling eukaryotic cell proliferation, apoptosis, and differentiation.

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Nucleocytoplasmic Trafficking of G2/M Regulators in Yeast

Molecular Biology of the Cell ◽

10.1091/mbc.e08-03-0286 ◽

2008 ◽

Vol 19 (9) ◽

pp. 4006-4018 ◽

Cited By ~ 25

Author(s):

Mignon A. Keaton ◽

Lee Szkotnicki ◽

Aron R. Marquitz ◽

Jake Harrison ◽

Trevin R. Zyla ◽

...

Keyword(s):

Cell Cycle ◽

Nuclear Import ◽

Nuclear Export ◽

Cell Cycle Regulators ◽

Cyclin Dependent Kinase ◽

Nucleocytoplasmic Trafficking ◽

Nucleocytoplasmic Shuttling ◽

Upstream Regulator ◽

Cellular Compartments ◽

Cdk Regulation

Nucleocytoplasmic shuttling is prevalent among many cell cycle regulators controlling the G2/M transition. Shuttling of cyclin/cyclin-dependent kinase (CDK) complexes is thought to provide access to substrates stably located in either compartment. Because cyclin/CDK shuttles between cellular compartments, an upstream regulator that is fixed in one compartment could in principle affect the entire cyclin/CDK pool. Alternatively, the regulators themselves may need to shuttle to effectively regulate their moving target. Here, we identify localization motifs in the budding yeast Swe1p (Wee1) and Mih1p (Cdc25) cell cycle regulators. Replacement of endogenous Swe1p or Mih1p with mutants impaired in nuclear import or export revealed that the nuclear pools of Swe1p and Mih1p were more effective in CDK regulation than were the cytoplasmic pools. Nevertheless, shuttling of cyclin/CDK complexes was sufficiently rapid to coordinate nuclear and cytoplasmic events even when Swe1p or Mih1p were restricted to one compartment. Additionally, we found that Swe1p nuclear export was important for its degradation. Because Swe1p degradation is regulated by cytoskeletal stress, shuttling of Swe1p between nucleus and cytoplasm serves to couple cytoplasmic stress to nuclear cyclin/CDK inhibition.

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