scholarly journals Serum-Induced Expression of the cdc25AGene by Relief of E2F-Mediated Repression

1999 ◽  
Vol 19 (7) ◽  
pp. 4695-4702 ◽  
Author(s):  
Xi Chen ◽  
Ron Prywes
Keyword(s):  
Cell Cycle ◽  
Point Mutation ◽  
Kinase Activity ◽  
Tyrosine Phosphatase ◽  
Retinoblastoma Protein ◽  
Early Gene ◽  
Cyclin Dependent Kinase ◽  
3T3 Cells ◽  
Induced Expression ◽  
Nih 3T3

ABSTRACT The cdc25A gene encodes a tyrosine phosphatase which activates cyclin-dependent kinase activity in the G1 phase of the cell cycle. cdc25A RNA levels are induced from 3 to 6 h after serum induction of serum-starved NIH 3T3 cells, suggesting that the cdc25A gene is a delayed-early gene. Analysis of cdc25A promoter constructs showed that thecdc25A promoter is sufficient for serum induction. Surprisingly for a gene expressed in early to mid-G1, serum induction of the promoter requires an E2F site at position −62 in the promoter. Deletion or point mutation of the E2F site resulted in activation of expression in serum-starved cells and no further induction by serum treatment. E2F factors were found to bind to thecdc25A E2F site along with the retinoblastoma protein (Rb) family members p130 and p107. A shift in mobility of the E2F-p107 complex in extracts of cells induced for 6 h correlated with induction of cdc25A expression. These results suggest that serum induction of cdc25A expression is mediated by inactivation of p107 or p130, both of which repress transcription when bound to the promoter through E2F.

scholarly journals Cyclin-Dependent Kinase Activity Is Required at Early Times for Accurate Processing and Accumulation of the Human Cytomegalovirus UL122-123 and UL37 Immediate-Early Transcripts and at Later Times for Virus Production

2004 ◽  
Vol 78 (20) ◽  
pp. 11219-11232 ◽  
Author(s):  
Veronica Sanchez ◽  
Anita K. McElroy ◽  
Judy Yen ◽  
Sama Tamrakar ◽  
Charles L. Clark ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Viral Replication ◽  
Human Cytomegalovirus ◽  
Kinase Activity ◽  
Hcmv Infection ◽  
Specific Inhibitor ◽  
Early Gene ◽  
Cyclin Dependent Kinase ◽  
Cyclin Dependent Kinases

ABSTRACT Human cytomegalovirus (HCMV) infection leads to dysregulation of multiple cell cycle-regulatory proteins. In this study, we examined the effects of inhibition of cyclin-dependent kinase (cdk) activity on viral replication. With the drug Roscovitine, a specific inhibitor of cyclin-dependent kinases 1, 2, 5, 7, and 9, we have shown that during the first 6 h of infection, cyclin-dependent kinase-dependent events occurred that included the regulated processing and accumulation of the immediate-early (IE) UL122-123 transcripts and UL36-37 transcripts. Altered processing of UL122-123 led to a loss of IE1-72 and an increase in IE2-86. The ratio of spliced to unspliced UL37 transcripts also changed. These effects did not require de novo protein synthesis or degradation of proteins by the proteasome. Addition of Roscovitine at the beginning of the infection was also associated with inhibition of expression of selected viral early gene products, viral DNA replication, and late viral gene expression. When Roscovitine was added after the first 6 h of infection, the effects on IE gene expression were no longer observed and viral replication proceeded through the late phase, but viral titers were reduced. The reduction in viral titer was observed even when Roscovitine was first added at 48 h postinfection, indicating that cyclin-dependent kinase activity is required at both IE and late times. Flavopiridol, another specific inhibitor of cyclin-dependent kinases, had similar effects on IE and early gene expression. These results underscore the importance of accurate RNA processing and reiterate the significant role of cell cycle-regulatory factors in HCMV infection.

Regulation of the junB gene by v-src

1992 ◽  
Vol 12 (8) ◽  
pp. 3356-3364
Author(s):  
I Apel ◽  
C L Yu ◽  
T Wang ◽  
C Dobry ◽  
M E Van Antwerp ◽  
...  
Keyword(s):  
Kinase Activity ◽  
Gene Products ◽  
3T3 Cells ◽  
Tyrosine Kinase Activity ◽  
Basal Expression ◽  
High Level ◽  
Transformed Cell Lines ◽  
Point Mutagenesis ◽  
Nih 3T3 ◽  
Nucleotide Region

The proteins encoded by cellular and viral src genes are believed to be involved in the transmission of mitogenic signals, the nuclear recipients of which are largely unknown. In this work, we report that four different v-src-transformed cell lines from three different species possess elevated levels of junB transcripts. Transient expression of junB promoter-chloramphenicol acetyltransferase constructs in NIH 3T3 cells was used to demonstrate that the increase in junB transcripts was specifically associated with v-src expression and could not be recapitulated with a c-src, v-H-ras, or v-raf expression vector. Deletion mutants were used to localize the v-src-responsive region in the junB promoter to a 121-nucleotide region encompassing the CCAAT and TATAA elements. This region is distinct from one in the 5' untranslated region of the junB gene which is required to maintain its high-level basal expression. Point mutagenesis of the junB TATAA box completely abolished v-src responsiveness, suggesting that proteins which bind to this element are modified by src transformation. Several v-src and c-src mutants were used to demonstrate that elevated tyrosine kinase activity of src proteins is required for the observed effects on junB expression. Finally, homology between the TATAA box regions of junB and the unrelated but src-responsive gene 9E3/CEF-4 suggests that modulation of gene activity through proteins which bind to this region may be a recurrent, although not exclusive, theme in src transforming action. Our results suggest that src proteins may modulate some nuclear effectors through pathways not involving cellular ras or raf gene products.

scholarly journals Cell cycle function of a Medicago sativa A2-type cyclin interacting with a PSTAIRE-type cyclin-dependent kinase and a retinoblastoma protein

2000 ◽  
Vol 23 (1) ◽  
pp. 73-83 ◽  
Author(s):  
Francois Roudier ◽  
Elena Fedorova ◽  
Janos Gyorgyey ◽  
Attila Feher ◽  
Spencer Brown ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Medicago Sativa ◽  
Retinoblastoma Protein ◽  
Cyclin Dependent Kinase

scholarly journals Human Papillomavirus Type 16 E7 Maintains Elevated Levels of the cdc25A Tyrosine Phosphatase during Deregulation of Cell Cycle Arrest

2002 ◽  
Vol 76 (2) ◽  
pp. 619-632 ◽  
Author(s):  
Don X. Nguyen ◽  
Thomas F. Westbrook ◽  
Dennis J. McCance
Keyword(s):  
Cell Cycle ◽  
Human Papillomavirus ◽  
Cell Cycle Arrest ◽  
Cell Cycle Progression ◽  
Tyrosine Phosphatase ◽  
Early Gene ◽  
Cycle Progression ◽  
Hpv 16 ◽  
Human Papillomavirus Type 16 ◽  
Cycle Arrest

ABSTRACT Essential to the oncogenic properties of human papillomavirus type 16 (HPV-16) are the activities encoded by the early gene product E7. HPV-16 E7 (E7.16) binds to cellular factors involved in cell cycle regulation and differentiation. These include the retinoblastoma tumor suppressor protein (Rb) and histone deacetylase (HDAC) complexes. While the biological significance of these interactions remains unclear, E7 is believed to help maintain cells in a proliferative state, thus establishing an environment that is conducive to viral replication. Most pathways that govern cell growth converge on downstream effectors. Among these is the cdc25A tyrosine phosphatase. cdc25A is required for G1/S transition, and its deregulation is associated with carcinogenesis. Considering the importance of cdc25A in cell cycle progression, it represents a relevant target for viral oncoproteins. Accordingly, the present study focuses on the putative deregulation of cdc25A by E7.16. Our results indicate that E7.16 can impede growth arrest induced during serum starvation and keratinocyte differentiation. Importantly, these E7-specific phenotypes correlate with elevated cdc25A steady-state levels. Reporter assays performed with NIH 3T3 cell lines and human keratinocytes indicate that E7 can transactivate the cdc25A promoter. In addition, transcriptional activation by E7.16 requires the distal E2F site within the cdc25A promoter. We further demonstrate that the ability of E7 to abrogate cell cycle arrest, activate cdc25A transcription, and increase cdc25A protein levels requires intact Rb and HDAC-1 binding domains. Finally, by using the cdk inhibitor roscovitine, we reveal that E7 activates the cdc25A promoter independently of cell cycle progression and cdk activity. Consequently, we propose that E7.16 can directly target cdc25A transcription and maintains cdc25A gene expression by disrupting Rb/E2F/HDAC-1 repressor complexes.

Nuclear localization of phosphatidylinositol 4-kinase β

2002 ◽  
Vol 115 (8) ◽  
pp. 1769-1775 ◽  
Author(s):  
Petra de Graaf ◽  
Elsa E. Klapisz ◽  
Thomas K. F. Schulz ◽  
Alfons F. M. Cremers ◽  
Arie J. Verkleij ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Kinase Activity ◽  
Insoluble Fraction ◽  
Type Ii ◽  
3T3 Cells ◽  
Type Iii ◽  
Pore Complexes ◽  
Phosphatidylinositol 4 ◽  
Nih 3T3 ◽  
Nih 3T3 Cells

Whereas most phosphatidylinositol 4-kinase (PtdIns 4-kinase) activity is localized in the cytoplasm, PtdIns 4-kinase activity has also been detected in membranedepleted nuclei of rat liver and mouse NIH 3T3 cells. Here we have characterized the PtdIns 4-kinase that is present in nuclei from NIH 3T3 cells. Both type II and type III PtdIns 4-kinase activity were observed in the detergent-insoluble fraction of NIH 3T3 cells. Dissection of this fraction into cytoplasmic actin filaments and nuclear lamina-pore complexes revealed that the actin filament fraction contains solely type II PtdIns 4-kinase,whereas lamina-pore complexes contain type III PtdIns 4-kinase activity. Using specific antibodies, the nuclear PtdIns 4-kinase was identified as PtdIns 4-kinase β. Inhibition of nuclear export by leptomycin B resulted in an accumulation of PtdIns 4-kinase β in the nucleus. These data demonstrate that PtdIns 4-kinase β is present in the nuclei of NIH 3T3 fibroblasts,suggesting a specific function for this kinase in nuclear processes.

scholarly journals Inactivation of CtIP Leads to Early Embryonic Lethality Mediated by G1 Restraint and to Tumorigenesis by Haploid Insufficiency

2005 ◽  
Vol 25 (9) ◽  
pp. 3535-3542 ◽  
Author(s):  
Phang-Lang Chen ◽  
Feng Liu ◽  
Suna Cai ◽  
Xiaoqin Lin ◽  
Aihua Li ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Transcriptional Repression ◽  
Cell Cycle Progression ◽  
Tumor Formation ◽  
3T3 Cells ◽  
Embryonic Fibroblasts ◽  
Cycle Progression ◽  
Early Embryonic Lethality ◽  
Nih 3T3 ◽  
Regulate Cell Cycle Progression

ABSTRACT CtIP interacts with a group of tumor suppressor proteins including RB (retinoblastoma protein), BRCA1, Ikaros, and CtBP, which regulate cell cycle progression through transcriptional repression as well as chromatin remodeling. However, how CtIP exerts its biological function in cell cycle progression remains elusive. To address this issue, we generated an inactivated Ctip allele in mice by inserting a neo gene into exon 5. The corresponding Ctip − / − embryos died at embryonic day 4.0 (E4.0), and the blastocysts failed to enter S phase but accumulated in G1, leading to a slightly elevated cell death. Mouse NIH 3T3 cells depleted of Ctip were arrested at G1 with the concomitant increase in hypophosphorylated Rb and Cdk inhibitors, p21. However, depletion of Ctip failed to arrest Rb − / − mouse embryonic fibroblasts (MEF) or human osteosarcoma Saos-2 cells at G1, suggesting that this arrest is RB dependent. Importantly, the life span of Ctip +/ − heterozygotes was shortened by the development of multiple types of tumors, predominantly, large lymphomas. The wild-type Ctip allele and protein remained detectable in these tumors, suggesting that haploid insufficiency of Ctip leads to tumorigenesis. Taken together, this finding uncovers a novel G1/S regulation in that CtIP counteracts Rb-mediated G1 restraint. Deregulation of this function leads to a defect in early embryogenesis and contributes, in part, to tumor formation.

Cell Cycle-Related Differences in Susceptibility of NIH/3T3 Cells to Ribonucleases

1999 ◽  
Vol 247 (1) ◽  
pp. 220-232 ◽  
Author(s):  
Mark R. Smith ◽  
Dianne L. Newton ◽  
Stanley M. Mikulski ◽  
Susanna M. Rybak
Keyword(s):  
Cell Cycle ◽  
3T3 Cells ◽  
Nih 3T3 ◽  
Nih 3T3 Cells
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