Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In normal human fibroblast cells, the primary cell cycle regulators, the cyclin-dependent kinases (CDKs), exist predominantly in multiple quaternary complexes, each consisting of a CDK, a cyclin, proliferating cell nuclear antigen (PCNA) and p21. p21 encodes a universal inhibitor of cyclin-dependent kinases. Here we show that the level of p21 mRNA and the interaction of p21 protein with cyclin-CDK enzymes are regulated during the cell cycle. When normal human fibroblast IMR90 cells were released from serum starvation, p21 mRNA reached its highest level immediately following serum stimulation, began to decrease at the G1/S boundary, fell to its lowest level during S phase, and accumulated again as cells exited from S phase. p21 protein associates with each cyclin-CDK complex in a cell cycle dependent manner. Cyclin A-CDK2-p21-PCNA and Cyclin B1-CDC2-p21-PCNA complexes are assembled in early S and G2 phase, respectively, indicating that p21 and/or PCNA regulates the enzymatic activity of each kinase at the time of their functioning. Cyclin D1-CDK4-p21-PCNA complexes, on the other hand, persist throughout the cell cycle, suggesting that cyclin D1-CDK4 quaternary complexes may play a role in monitoring an event(s) that may occur at any time, rather than at a specific stage of the cell cycle. The level of p21 mRNA in early passage Li-Fraumeni cells that are heterozygous for p53 mutation remained similar to that in normal fibroblasts, but was undetectable in immortalized Li-Fraumeni cells homozygous for mutant p53. This finding provides a plausible molecular explanation for the loss of genetic stability associated with cells homozygous, but not heterozygous, for p53 mutation.
 ...
PMID:Cell cycle expression and p53 regulation of the cyclin-dependent kinase inhibitor p21. 791 44

In this study we have surveyed by immunoblotting the protein levels of Cyclin D1, D2, D3 and their catalytic partners, Cdk4 and Cdk6 in normal and transformed human cells. We found that all these proteins were differentially expressed in diploid cells derived from different tissues, in contrast to Cyclin E, Cyclin A and Cdk2 which are ubiquitously expressed. D-type Cyclins were never dramatically overexpressed and often very poorly expressed in tumor cell lines when compared to the levels in their normal counterparts. In contrast, Cdk4 was expressed at high levels in several tumor cell lines and Cdk6 was ectopically expressed in two sarcoma lines, suggesting a possible involvement of these two Cdks in oncogenesis. Interestingly, low levels of Cyclin D1 and D3 proteins always correlated with functional inactivation of the retinoblastoma gene product (pRb). In cells displaying active pRb, Cyclin D1 was found associated with Cdk4 regardless of whether the p53 gene was wild-type or mutant. Microinjection during G1 of Cyclin D1 anti-sense cDNA or anti-Cyclin D1 antibody in these cells arrested the cell cycle in G1. In cells lacking pRb function, Cyclin D1 was dissociated from Cdk4. Microinjection during G1 of Cyclin D1 antisense cDNA or anti-Cyclin D1 antibody in these cells did not affect G1 progression. These results show that (i) in the absence of pRb, Cyclin D1 is expressed at low levels, is dissociated from Cdk4 and becomes dispensable in G1; (ii) Cyclin D1 needs to be associated with its catalytic subunit, Cdk4, to function as a positive regulator of G1 progression.
 ...
PMID:Differential expression and regulation of Cyclin D1 protein in normal and tumor human cells: association with Cdk4 is required for Cyclin D1 function in G1 progression. 805 30

Sympathetic neurons undergo RNA and protein synthesis-dependent programmed cell death when deprived of nerve growth factor. To test the hypothesis that neuronal programmed cell death is a consequence of conflicting growth signals which cause the inappropriate activation of cell cycle genes, we have analyzed cell cycle-related genes for their expression in postmitotic neurons. Surprisingly, many of these genes are expressed in neurons, although cdc2, cdk2, and cyclin A are not. During programmed cell death, the expression of most of these genes, including several cyclins and the Rb and p53 tumor suppressor genes, decreases similar to that of neuronal genes. In contrast, cyclin D1 expression is selectively induced in dying neurons. Cyclin D1 mRNA levels peak 15-20 hr after nerve growth factor withdrawal, concurrent with the time that neurons become committed to die. These results provide an extensive characterization of cell cycle gene expression in postmitotic neurons and provide the evidence for a gene induced during neuronal programmed cell death.
 ...
PMID:Analysis of cell cycle-related gene expression in postmitotic neurons: selective induction of Cyclin D1 during programmed cell death. 811 Apr 63

Defects in cell cycle control and increased genomic instability, including gene amplification, often occur during cancer development. Cyclin D1 plays a pivotal role in G1, and this gene is frequently amplified and overexpressed in several types of human cancer. This study demonstrates that ectopic overexpression of cyclin D1 in a rat liver epithelial cell line markedly increased the yield of cells containing amplified copies of the CAD gene. This effect was associated with a loss of G1-S checkpoint control, although the cyclin D1-overexpressing cells had a normal p53 gene. The capacity of cyclin D1 to enhance gene amplification may contribute to the process of genomic instability during tumor development.
 ...
PMID:Overexpression of cyclin D1 enhances gene amplification. 854 70

Cyclin D1 is one of the key regulators in G1 progression in the cell cycle and is also a candidate oncogene (termed PRAD1 or bcl-1) in several types of human tumors. We report a collaboration of the cyclin D1 gene with ras and a mutated form of p53 (p53-mt) in neoplastic transformation. Transfection of cyclin D1 alone or in combination with ras or with p53-mt was not sufficient for focus formation of rat embryonic fibroblasts. However, focus formation induced by co-transfection of ras and p53-mt was enhanced in the presence of the cyclin D1-expression plasmid. Co-transfection of ras- and p53-mt-transformants with the cyclin D1-expression plasmid resulted in reduced serum dependency in vitro. Furthermore, the transformants expressing exogenous cyclin D1 grew faster than those without the cyclin D1 plasmid when injected into nude mice. These observations strengthen the significance of cyclin D1 overexpression through gene rearrangement or gene amplification observed in human tumors as a step in multistep oncogenesis; deregulated expression of cyclin D1 may reduce the requirement for growth factors and may stimulate in vivo growth.
 ...
PMID:Oncogenic collaboration of the cyclin D1 (PRAD1, bcl-1) gene with a mutated p53 and an activated ras oncogene in neoplastic transformation. 864 82

The prognostic factors for esophageal cancer from the viewpoint of molecular biology are reviewed. Among several oncogenes and suppressor genes erbB, int2/hst1/Cyclin D1 and MDM2 gene amplifications are significant prognostic factors for esophageal cancer. The value of p53 mutation, and expression of matrix metalloproteinase (MMPs) in the prediction of patients' survival are controversial, so further research is needed. High expression of tumor proliferation-related factors (Ki67, PCNA, and AgNOR), abnormalities of adhesion molecule (E-Cadherin, alpha-Catenin), activation of autocrine mechanism of growth factor (EGFR-TGF alpha, EGF), and DNA ploidy pattern, which is thought to be the result of an accumulation of genomic abnormalities are also prognostic factors for esophageal cancer.
 ...
PMID:[Prognostic factors for esophageal cancer--from the viewpoint of molecular biology]. 868 32

Various molecular genetic abnormalities have been reported in esophageal carcinoma. These include amplification of the chromosome 11q13 region containing cyclin D1, EXP1 and EMS1 genes, and the oncogenes, the epidermal growth factor receptor gene, EGFR/c-ERBB1, and c-myc. Loss of heterozygosity (LOH) at several chromosome loci and point mutation of the p53 and p16/CDKN2 tumor suppressor genes have also been described. Mutations of p53 gene and LOH at 3p and 9q loci were investigated in esophageal epithelial dysplasia. In contrast, amplification of cyclin D1, EGFR, c-myc and other genes was accumulated in advanced tumors with invasion. Cyclin D1 amplification is found more in metastatic lesions than in primary tumors.
 ...
PMID:[Genetic events during development of esophageal squamous cell carcinoma]. 892 Jun 74

Recent evidence has implicated aberrant cell cycle regulation as a possible mechanism of apoptosis in non-dividing cells. We previously demonstrated increased expression of the p53 tumor suppressor gene, a prominent cell cycle regulator, in apoptotic neurons. Here we investigated the potential involvement of cyclin D1, a G1 phase cell cycle protein under p53 regulation, in kainic acid-mediated neuronal degeneration. Adult male Sprague-Dawley rats were treated systemically with kainic acid and sacrificed between 1 h and 5 days following seizure onset. Cyclin D1 expression was studied by Western blot analysis and immunohistochemistry using a rabbit polyclonal anti-cyclin D1 antibody. In untreated control rats low levels of cyclin D1 expression were detected in multiple brain regions. Between 8 and 16 h after the onset of kainic acid-induced seizures, increased cyclin D1 immunoreactivity was observed in vulnerable hippocampal pyramidal cells. Five days after seizure onset increased cyclin D1 expression was evident in reactive astrocytes. These results support a role for cyclin D1 in certain neuronal death pathways, and suggest that cyclin D1 has multiple and cell type-specific functions in the central nervous system.
 ...
PMID:Increased expression of cyclin D1 in the adult rat brain following kainic acid treatment. 898 68

Cyclin D1 plays a key regulatory role during the G1 phase of the cell cycle and its gene is amplified and overexpressed in many cancers. To address the relationship between cyclin D1 and other cell cycle regulatory proteins, we established human glioma and rodent fibroblast cell lines in which cyclin D1 expression could be regulated ectopically with tetracycline. In both of these cell lines, we found that ectopic expression of cyclin D1 in asynchronously growing cells was accompanied by increased levels of the p53 tumor suppressor protein and the cyclin/cdk inhibitor p21. Despite the induction of these cell cycle inhibitory proteins, cyclin D1-associated cdk kinase remained activated and the cells grew essentially like that of the parent cells. Although growth parameters were unchanged in these cells, morphological changes were clearly identifiable and anchorage independent growth was observed in NIH3T3 cells. In a first step toward elaborating the mechanism for cyclin D1-mediated induction of p21 gene expression we show that co-expression of E2F-1 and DP-1 can specifically transactivate the p21 promoter. In support of these findings and a direct effect of E2F on induction of p21 gene expression a putative E2F binding site was identified within the p21 promoter. In summary, our results demonstrate that ectopic expression of cyclin D1 can induce gene expression of the cdk inhibitor p21 through an E2F mechanism the consequences of which are not to growth arrest cells but possibly to stabilize cyclin D1/cdk function.
 ...
PMID:Regulated ectopic expression of cyclin D1 induces transcriptional activation of the cdk inhibitor p21 gene without altering cell cycle progression. 919 Oct 53

Human papillomavirus (HPV) DNA has been detected in approximately 15% of squamous cell carcinomas (SCCs) of the head and neck. Recent studies have shown a predilection of HPV for certain anatomical sites, especially the tonsillar region, with viral DNA identified in approximately 60% of SCCs of the Waldeyer's tonsillar ring. This study was undertaken to determine whether there are differences in morphology or in oncogene expression in SCC of the tonsil with and without detectable HPV DNA. Twenty-two SCCs of the tonsil were analyzed for the presence of HPV DNA by polymerase chain reaction (PCR) using both a consensus primer set (My09/My11) and type-specific primers. Viral transcription was established in both primary and metastatic tumors by RNA in situ hybridization. The morphology of invasive SCC was classified into three subtypes: well keratinized (K-SCC), intermediate keratinized (I-SCC), and poorly keratinized (P-SCC). Expression of p53, pRB, and cyclin D1 (bcl-1) were studied by immunohistochemistry. In these cases (6 K-SCCs, 2 I-SCCs, and 14 P-SCCs), HPV DNA was detected in 14 (64%), with 11 containing HPV-16 (10 P-SCCs, 1 I-SCCs, and 0 K-SCCs) and 1 each containing HPV-33, HPV-59, and an unclassified HPV type (all P-SCCs). Viral oncoprotein E6/E7 transcription was demonstrated in 7 of 7 HPV-16-positive tumors. Cyclin D1 protein overexpression was detected in the majority of HPV-negative tumors (7 of 8 cases), whereas it was minimal or absent in 13 HPV-positive tumors. Overexpression of p53 protein was detected in 3 HPV-negative K-SCCs. In the HPV-positive tumors, fewer malignant cells expressed pRB and the staining was less intense than in the HPV-negative cancers. HPV DNA and E6/E7 expression, especially HPV-16, is detected in the majority of tonsillar SCCs and is almost exclusively associated with a poorly keratinized tumor histology. Decreased expression of cyclin D1, pRB, and p53 in tumors with HPV DNA is consistent with the known effects of the viral oncoproteins on the cellular protein. The morphology of the HPV-positive tumors suggests that HPV may have a predilection for a population of nonkeratinizing squamous cells or that the virally transformed cells inhibit keratinization of the tumor cells. Well keratinized tonsillar SCCs lack HPV DNA and are associated with overexpression of cyclin D1 protein and/or p53, suggesting that mechanisms that alter the cell cycle regulatory proteins, either by interaction with viral oncoproteins or by changes in the cellular proteins themselves, is critical for tumorigenesis of tonsillar SCC.
 ...
PMID:Detection of human papillomavirus DNA and oncoprotein overexpression are associated with distinct morphological patterns of tonsillar squamous cell carcinoma. 942 32


1 2 3 4 5 6 7 8 9 10 Next >>