The stimulation of thyroid cell proliferation by TSH through cAMP depends on permissive comitogenic factors, generally the insulin-like growth factors and insulin. In dog thyroid primary cultures, the use of the phosphodiesterase-resistant analog of cAMP (Bu)(2)cAMP instead of TSH allowed to unveil a potent comitogenic activity of carbamylcholine, which can substitute for insulin and was shown to mimic insulin action on cell cycle regulatory proteins. Like insulin, carbamylcholine induced the accumulation of cyclin D3 and overcame the repression by cAMP of this protein, which was shown 1) to be essential for cell cycle progression by means of microinjections of a neutralizing antibody; and 2) to be rate limiting for the cAMP-dependent assembly of cyclin D3-cdk4 complexes, their nuclear translocation and the phosphorylation of pRb. Relative to insulin, carbamylcholine offers the significant experimental advantage that its signaling cascades can be immediately deactivated by the muscarinic antagonist atropine. In the presence of carbamylcholine, the elimination of (Bu)(2)cAMP blocked within 2 h the entry of cells into DNA synthesis phase, but the addition of atropine still permitted the entry of cells in S phase. These data support our view that the progression in G1 phase stimulated by cAMP consists of at least two essential actions that are clearly dissociated: in a first stage, depending on the supportive activity of an agent that stimulates the required cyclin D3 accumulation, cAMP induces the assembly and nuclear translocation of cyclin D3-cdk4 complexes, and then cAMP can exert alone the last crucial control that determines the cell commitment toward DNA replication.
- MeSH
- AMP cyklický * fyziologie MeSH
- buněčné jádro metabolismus MeSH
- buněčný cyklus fyziologie účinky záření MeSH
- cyklin D3 MeSH
- cyklin-dependentní kinasa 4 MeSH
- cyklin-dependentní kinasy fyziologie MeSH
- cykliny fyziologie MeSH
- dibutyryl cyklický AMP farmakologie MeSH
- DNA biosyntéza MeSH
- G1 fáze MeSH
- hypertrofie MeSH
- karbachol * farmakologie metabolismus MeSH
- kultivované buňky MeSH
- mitóza účinky léků MeSH
- proteiny buněčného cyklu fyziologie MeSH
- protoonkogenní proteiny * MeSH
- psi MeSH
- štítná žláza * cytologie metabolismus patologie účinky léků MeSH
- synergismus léků MeSH
- zvířata MeSH
- Check Tag
- psi MeSH
- zvířata MeSH
- MeSH
- buněčný cyklus fyziologie genetika MeSH
- cykliny fyziologie genetika MeSH
- nádory patofyziologie MeSH
- Publikační typ
- přehledy MeSH
- Klíčová slova
- OLOMOUCIN, FLAVOPIRIDOL,
- MeSH
- adenin analýza terapeutické užití MeSH
- buněčné dělení fyziologie MeSH
- cykliny fyziologie MeSH
- fosforylace MeSH
- inhibitory syntézy proteinů MeSH
- lidé MeSH
- nádory terapie MeSH
- Check Tag
- lidé MeSH
Human herpesvirus-8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus, encodes a protein, referred to as HHV8-Vcyc, with sequence similarity to human G1 cyclins, in particular of the D type. HHV8-Vcyc is expressed in Kaposi's sarcoma and functional analysis suggests that it can activate cyclin-dependent kinases (cdk) and thereby trigger inactivation of the retinoblastoma protein (pRb), indicating that HHV8-Vcyc may contribute to the oncogenic potential of HHV-8. We show here that HHV8-Vcyc can activate transcription of the human cyclin A gene in quiescent cells, a property shared with known transforming oncogenes. Transcriptional activation by HHV8-Vcyc depends on an E2F-binding site in the cyclin A promoter, and cdk6 kinase activity is required. The ability of HHV8-Vcyc to activate cyclin A gene expression is shared by D-type cyclins and cyclin E. Unlike D-type cyclins, HHV8-Vcyc is unable to trigger phosphorylation of the pRb-related protein p107 and fails to induce dissociation of p107 from E2F. Unlike cyclin E, HHV8-Vcyc fails to interact physically with E2F complexes on the cyclin A promoter. These results provide additional evidence for the notion that the HHV-8-encoded cyclin differs in several properties from cellular G1 cyclins.
- MeSH
- aktivace transkripce * MeSH
- buňky 3T3 MeSH
- cyklin A genetika metabolismus MeSH
- cyklin-dependentní kinasa 6 MeSH
- cyklin-dependentní kinasy * MeSH
- cykliny genetika fyziologie MeSH
- DNA vazebné proteiny genetika metabolismus MeSH
- fosforylace MeSH
- jaderné proteiny genetika metabolismus MeSH
- lidé MeSH
- lidský herpesvirus 8 genetika fyziologie MeSH
- myši MeSH
- nádorové buňky kultivované MeSH
- precipitinové testy MeSH
- promotorové oblasti (genetika) genetika MeSH
- protein p107 podobný retinoblastomu MeSH
- protein-serin-threoninkinasy metabolismus MeSH
- proteiny buněčného cyklu genetika metabolismus MeSH
- rekombinantní fúzní proteiny metabolismus MeSH
- sekvenční homologie aminokyselin MeSH
- transkripční faktor DP1 MeSH
- transkripční faktor E2F4 MeSH
- transkripční faktory genetika metabolismus MeSH
- vazba proteinů MeSH
- virové proteiny genetika fyziologie MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The cyclin-dependent kinase (CDK) inhibitor p21WAF1/CIP1 is a multidomain, multifunctional protein and a candidate tumor suppressor. Here, we show that, among rationally designed and tumor-associated mutants of human p21 ectopically expressed in U-2-OS cells, those that are selectively deficient in binding to either cyclin or CDK are partially impaired in inhibiting endogenous CDK activities but efficiently promote assembly of active cyclin D/CDK4(6) complexes. These results provide mechanistic insights into the p21-cyclin/CDK interplay in vivo and suggest a functional subclassification of tumor-specific aberrations of p21. Intriguingly, the subclass exemplified by the melanoma-derived N50S mutant may promote tumorigenesis, by both attenuating CDK-inhibitory function and concomitantly activating the proto-oncogenic cyclin D-dependent kinases.
- MeSH
- bodová mutace MeSH
- cyklin D MeSH
- cyklin-dependentní kinasa 4 MeSH
- cyklin-dependentní kinasa 6 MeSH
- cyklin-dependentní kinasy metabolismus MeSH
- cykliny genetika metabolismus fyziologie MeSH
- inhibitor p21 cyklin-dependentní kinasy MeSH
- lidé MeSH
- melanom metabolismus MeSH
- nádorové buňky kultivované MeSH
- nádorové proteiny genetika fyziologie MeSH
- protein-serin-threoninkinasy metabolismus MeSH
- protoonkogenní proteiny * MeSH
- tumor supresorové geny MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The mammalian D-type cyclins D1, D2, and D3 activate the cyclin-dependent kinases CDK4 and CDK6 in G1 and thereby promote the cell's commitment to enter S phase. To elucidate the extent of functional overlap among the D-type cyclins, we have examined several aspects of the least characterized member of this subfamily of G cyclin proteins, cyclin D3. Microinjection of cyclin D3-neutralizing antibody inhibited G1/S transition in human (IMR-90) and rat (R12) diploid fibroblasts, indicating that analogous to cyclins D1 and D2, cyclin D3 is essential for timely progression through G1. In contrast to cyclins D1 and D2, cyclin D3 was (i) ubiquitously expressed among a panel of 70 human cultured cell types; (ii) strongly upregulated upon induction of HL-60 leukaemia cells to differentiate; and (iii) accumulated to high levels in a wide range of quiescent cell types in mouse and human differentiated tissues. Complementary analyses of human biopsies and mouse tissues at different stages of foetal and postnatal development revealed lineage-dependent transient or long-term accumulation of the cyclin D3 protein, correlating with initiation/establishment or maintenance of the mature phenotypes, respectively. Our data support the notion that the biological roles of the individual D-type cyclins are not fully redundant, and suggest a possible dual role for cyclin D3 in cell proliferation and induction and/or maintenance of terminal differentiation.
- MeSH
- akutní promyelocytární leukemie patologie MeSH
- buněčná diferenciace fyziologie MeSH
- buněčné dělení fyziologie MeSH
- buněčné linie MeSH
- cyklin D3 MeSH
- cykliny biosyntéza imunologie fyziologie MeSH
- G1 fáze fyziologie MeSH
- HL-60 buňky MeSH
- interfáze fyziologie MeSH
- kosterní svaly cytologie metabolismus MeSH
- lidé MeSH
- monoklonální protilátky chemie MeSH
- nádorové buňky kultivované MeSH
- orgánová specificita MeSH
- S fáze fyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
We demonstrate in this paper that CDK4 which is a G1 phase specific cell cycle regulator and catalytic subunit of D-type cyclins has oncogenic activity similar to D-type cyclins themselves and is able to provoke focus formation when cotransfected with activated Ha-ras into primary rat embryo fibroblasts. Surprisingly, using two different mutants we show that CDK4's ability to bind to p16INK4a and not its kinase activity is important for its transforming potential. In addition, p16INK4a but not a mutant form that is found in human tumours can completely abrogate focus formation by CDK4 suggesting that CDK4 can malignantly transform cells by sequestering p16INK4a or other CKIs. We demonstrate that both cyclin D1 and CDK4 functionally depend on active Myc to exert their potential as oncogenes and vice versa that the transforming ability of Myc requires functional cyclin D/CDK complexes. Moreover, we find that p16INK4a and the Rb related protein p107 which releases Myc after phosphorylation by cyclin D1/CDK4 efficiently block Myc's activity as a transcriptional transactivator and as an oncogene. We conclude that both p16INK4a and cyclin D/CDK4 complexes are upstream regulators of Myc and directly govern Myc function in transcriptional transactivation and transformation via the pocket protein p107.
- MeSH
- aktivace transkripce MeSH
- buňky 3T3 MeSH
- cyklin D1 MeSH
- cyklin-dependentní kinasa 4 MeSH
- cyklin-dependentní kinasy fyziologie MeSH
- cykliny fyziologie MeSH
- geny myc fyziologie MeSH
- HeLa buňky MeSH
- inhibitor p16 cyklin-dependentní kinasy MeSH
- krysa rodu rattus MeSH
- lidé MeSH
- myši MeSH
- nádorová transformace buněk * MeSH
- onkogenní proteiny fyziologie MeSH
- potkani inbrední F344 MeSH
- protoonkogenní proteiny * MeSH
- retinoblastomový protein fyziologie MeSH
- transportní proteiny fyziologie MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- lidé MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
