Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The 86 kDa immediate early IE2 protein of human cytomegalovirus (HCMV) can activate transcription of both viral and cellular genes and can repress transcription from its own promoter. Using two in vivo assays, we provide evidence of a functional interaction between IE2 and the retinoblastoma (RB) protein: IE2 alleviates RB-induced repression of a promoter bearing E2F binding sites and RB alleviates IE2-mediated repression of its own promoter. These functional effects are likely to be a result of a direct contact between IE2 and RB, which we can demonstrate both in vitro and in HCMV-infected cells. The interaction between IE2 and RB shows similar characteristics to the interaction between RB and E1A. First, binding to IE2 requires an intact RB pocket domain. Secondly, the binding is sensitive to the phosphorylation state of RB, because cyclin A-CDK-induced phosphorylation of RB diminishes IE2 binding. Thirdly, the IE2 domain required for RB binding is separate to the domains necessary for TBP and TFIIB binding. Our results demonstrate that large and small DNA viruses have a common interface with the host cell, namely the association with the RB tumour suppressor protein.
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PMID:Functional interaction between the HCMV IE2 transactivator and the retinoblastoma protein. 802 74

The pocket domain of the retinoblastoma (Rb) tumour suppressor is central to Rb function, and is frequently inactivated by the binding of the human papilloma virus E7 oncoprotein in cervical cancer. The crystal structure of the Rb pocket bound to a nine-residue E7 peptide containing the LxCxE motif, shared by other Rb-binding viral and cellular proteins, shows that the LxCxE peptide binds a highly conserved groove on the B-box portion of the pocket; the A-box portion appears to be required for the stable folding of the B box. Also highly conserved is the extensive A-B interface, suggesting that it may be an additional protein-binding site. The A and B boxes each contain the cyclin-fold structural motif, with the LxCxE-binding site on the B-box cyclin fold being similar to a Cdk2-binding site of cyclin A and to a TBP-binding site of TFIIB.
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PMID:Structure of the retinoblastoma tumour-suppressor pocket domain bound to a peptide from HPV E7. 949 40

Entry into mitosis is accompanied by a global repression of transcription. To investigate the molecular mechanisms which shut-down rRNA synthesis during mitosis, we have compared RNA polymerase I (Pol I) transcription in extracts from asynchronous and mitotic HeLa cells. We show by several experimental approaches that phosphorylation by cdc2/cyclin B inactivates the TBP-containing factor SL1 and thus abrogates Pol I transcription during mitosis. This finding links the cell's cycle with the transcriptional activity of Pol I and suggests a common mechanism for mitotic silencing of all three classes of nuclear RNA polymerases, i.e. reversible inactivation of the respective TBP-TAF complexes by (a) mitotic kinase(s).
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PMID:Mitotic phosphorylation of the TBP-containing factor SL1 represses ribosomal gene transcription. 981 37

We have used a reconstituted cell-free transcription system to investigate the molecular basis of mitotic repression of RNA polymerase I (pol I) transcription. We demonstrate that SL1, the TBP-containing promoter-binding factor, is inactivated by cdc2/cyclin B-directed phosphorylation, and reactivated by dephosphorylation. Transcriptional inactivation in vitro is accompanied by phosphorylation of two subunits, e.g. TBP and hTAFI110. To distinguish whether transcriptional repression is due to phosphorylation of TBP, hTAFI110 or both, SL1 was purified from two HeLa cell lines that express either full-length or the core domain of TBP only. Both TBP-TAFI complexes exhibit similar activity and both are repressed at mitosis, indicating that the variable N-terminal domain which contains multiple target sites for cdc2/cyclin B phosphorylation is dispensable for mitotic repression. Protein-protein interaction studies reveal that mitotic phosphorylation impairs the interaction of SL1 with UBF. The results suggest that phosphorylation of SL1 is used as a molecular switch to prevent pre-initiation complex formation and to shut down rDNA transcription at mitosis.
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PMID:Mitotic silencing of human rRNA synthesis: inactivation of the promoter selectivity factor SL1 by cdc2/cyclin B-mediated phosphorylation. 985 93

Mitosis involves a generalized repression of gene expression. In the case of RNA polymerase III transcription, this is due to phosphorylation-mediated inactivation of TFIIIB, an essential complex comprising the TATA-binding protein TBP and the TAF subunits Brf1 and Bdp1. In HeLa cells, this repression is mediated by a mitotic kinase other than cdc2-cyclin B and is antagonized by protein phosphatase 2A. Brf1 is hyperphosphorylated in metaphase-arrested cells, but remains associated with promoters in condensed chromosomes, along with TBP. In contrast, Bdp1 is selectively released. Repression can be reversed by raising the concentration of Brf1 or Bdp1. The data support a model in which hyperphosphorylation disrupts TFIIIB during mitosis, compromising its ability to support transcription.
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PMID:TFIIIB is phosphorylated, disrupted and selectively released from tRNA promoters during mitosis in vivo. 1459 81

Doxorubicin (DOX) is a DNA topoisomerase II inhibitor widely used in anticancer treatment, however, it can lead to irreversible cardiac damage with severe debilitation. TBP-binding associated factor 1 (TAF1) is increased in DOX damaged hearts in vivo and in cardiomyocytes in vitro. To identify the functional role for TAF1 in DOX-treated heart we overexpressed wild type and mutant TAF1 in H9c2 cells. Overexpression of wild-type TAF1, but not N-terminal kinase domain mutants, increased tolerance to DOX in confluent cells. DOX treatment can cause prolonged G1 arrest. We found increased cdk2 activity coupled to increased cyclin E protein and decreased p21(waf1Cip1) and p27(Kip1) protein to correlate only with increased DOX tolerance and wild-type TAF1. DOX sensitivity was restored when the cdk2-inhibitor Roscovitine was co-administered with DOX. Overexpression of cdk2-alone increased resistance to DOX. Thus, TAF1 induced DOX tolerance in confluent cells through an increase in cdk2 activity is directed by the TAF1 N-terminal domain. These studies suggest new avenues for myocardial protection against DOX toxicity and suggest a role for cdk2 in chemorefractory cells.
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PMID:TBP-associated factor 1 overexpression induces tolerance to Doxorubicin in confluent H9c2 cells by an increase in cdk2 activity and cyclin E expression. 1512 10

Human immunodeficiency virus type 1 (HIV-1) Tat transactivation is an essential step in the viral life cycle. Over the past several years, it has become widely accepted that Tat exerts its transcriptional effect by binding the transactivation-responsive region (TAR) and enhancing transcriptional elongation. Consistent with this hypothesis, it has been shown that Tat promotes the binding of P-TEFb, a transcription elongation factor composed of cyclin T1 and cdk9, and the interaction of Tat with P-TEFb and TAR leads to hyperphosphorylation of the C-terminal domain (CTD) of RNA Pol II and increased processivity of RNA Pol II. A recent report, however, has generated renewed interest that Tat may also play a critical role in transcription complex (TC) assembly at the preinitiation step. Using in vivo chromatin immunoprecipitation assays, the authors reported that the HIV TC contains TBP but not TBP-associated factors. The stimulatory effect involved the direct interaction of Tat and P-TEFb and was evident at the earliest step of TC assembly, the TBP-TATA box interaction. In this article, we will review this data in context of earlier data which also support Tat's involvement in transcriptional complex assembly. Specifically, we will discuss experiments which demonstrated that Tat interacted with TBP and increased transcription initiation complex stability in cell free assays. We will also discuss studies which demonstrated that over expression of TBP alone was sufficient to obtain Tat activated transcription in vitro and in vivo. Finally, studies using self-cleaving ribozymes which suggested that Tat transactivation was not compatible with pausing of the RNA Pol II at the TAR site will be discussed.
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PMID:Tat gets the "green" light on transcription initiation. 1628 76

The Mediator complex (Mediator) is conserved among eukaryotes and is comprised of head, middle, tail and CDK/cyclin modules. The head module has received the most attention because its interaction with RNA polymerase II (Pol II) and the general transcription factors TFIIH and TBP facilitates phosphorylation of the carboxy-terminal domain (CTD) of the largest subunit of Pol II. We studied the human head module subunit hMED18 to elucidate how Mediator is involved in both transcriptional activation and repression. siRNA-mediated hMED18 depletion augmented transcription, indicating that hMED18 functions in transcriptional repression. Treatment of cells with two histone deacetylase (HDAC) inhibitors, the HDAC inhibitor trichostatin A (TSA) and the SIRT inhibitor nicotinamide showed that this repression was not caused by those HDAC activities. A screen for hMED18-target genes showed that the promoters for cap RNA methyltransferase RNMT-activating mini protein (RAM/FAM103A1) and divalent metal transporter 1 (DMT1/SLC11A2) genes were bound by hMED18. Depletion of hMED18 showed hMED18 and the middle module subunit hMED1 were lost from the promoters of those genes, whereas the CDK/cyclin module subunit hCDK8 remained bound. This indicates a novel transcriptional repression mechanism of hMED18 mediated by hCDK8 and further a novel positive role of free CDK/cyclin module in transcriptional activation. [Correction added on 12 June 2014, after first online publication: SLC11A2 amended from SCL11A2.].
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PMID:Mediator MED18 subunit plays a negative role in transcription via the CDK/cyclin module. 2484 Sep 24

In eukaryotes, holo-Mediator consists of four modules: head, middle, tail, and CDK/Cyclin. The head module performs an essential function involved in regulation of RNA polymerase II (Pol II). We studied the human head module subunit MED17 (hMED17). Recent structural studies showed that yeast MED17 may function as a hinge connecting the neck and movable jaw regions of the head module to the fixed jaw region. Luciferase assays in hMED17-knockdown cells showed that hMED17 supports transcriptional activation, and pulldown assays showed that hMED17 interacted with Pol II and the general transcription factors TFIIB, TBP, TFIIE, and TFIIH. In addition, hMED17 bound to a DNA helicase subunit of TFIIH, XPB, which is essential for both transcription and nucleotide excision repair (NER). Because hMED17 associates with p53 upon UV-C irradiation, we treated human MCF-7 cells with either UV-C or the MDM2 inhibitor Nutlin-3. Both treatments resulted in accumulation of p53 in the nucleus, but hMED17 remained concentrated in the nucleus in response to UV-C. hMED17 colocalized with the NER factors XPB and XPG following UV-C irradiation, and XPG and XPB bound to hMED17 in vitro. These findings suggest that hMED17 may play essential roles in switching between transcription and NER.
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PMID:Human mediator MED17 subunit plays essential roles in gene regulation by associating with the transcription and DNA repair machineries. 2548 73