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)

We have identified the phosphorylation sites in monkey p53 as well as specific changes in the phosphorylation state of free and complexed forms of simian virus 40 (SV40) large T antigen (T) and monkey p53 isolate from SV40 lytically infected CV1 cells. Phosphopeptide analyses of free T and p53 (To and p53o) and complexed T and p53 (T+ and p53+) fractions indicated several quantitative increases in the specific phosphorylation of complexed forms of both proteins. The N terminus of monkey p53+ is phosphorylated at Ser-9, Ser-15, Ser-20, either Ser-33 or Ser-37, and at least one of Ser-90 to Ser-99. The C-terminal sites are Ser-315 and Ser-392. On comparing p53+ with p53o, we found that labeling of the two N-terminal phosphotryptic peptides encompassing residues 1 to 20 and 33 to 101 was increased fivefold and that Ser-315 was sevenfold more labeled than was Ser-392. When T+ was compared with To, the N-terminal peptide containing phosphorylation sites Ser-106 through Thr-124 was twofold more labeled, the peptide containing Ser-657 through Ser-679 was sixfold more labeled and contained up to four phosphorylated serine residues, and Ser-639 and Thr-701 appeared unchanged. Overall, T+ molecules appeared to contain 3.5 mol more of labeled phosphate than did To, with the N-terminal peptide appearing fully phosphorylated. The phosphopeptide patterns obtained for lytic T+ and To fractions were nearly identical to those found for wild-type SV40 T (stably complexed with mouse p53) and mutant 5080 T (defective for p53 binding) expressed in transformed C3H10T1/2 cells (L. Tack, C. Cartwright, J. Wright, A. Srinivasan, W. Eckhart, K. Peden, and J. Pipas, J. Virol. 63:3362-3367, 1989). These results indicate that increases in specific phosphorylation sites in both T+ and p53+ correlate with the association of T with p53. The enhanced phosphorylation state may be a consequence of complex formation between T and p53 or reflect an increased affinity of p53 for highly phosphorylated forms of T.
 ...
PMID:Altered phosphorylation of free and bound forms of monkey p53 and simian virus 40 large T antigen during lytic infection. 131 Jul 51

We have analyzed in detail the phosphorylation of p53 from normal (3T3) and simian virus 40 (SV40)-transformed (SV3T3) BALB/c mouse cells and from normal (F111) and SV40-transformed [FR(wt648)] rat cells by two-dimensional tryptic peptide mapping and phosphoamino acid analyses. To accommodate the different half-lives of p53 in normal (half-life, 15 min) and transformed (half-life, 20 h) cells and possible differences in the rates of turnover of phosphate at specific sites, cells were labeled for 2 h (short-term labeling) or 18 h (long-term labeling). Depending on the labeling conditions, either close similarities or marked differences were observed in the phosphorylation patterns of p53 from normal and transformed cells. After the 2-h labeling, the phosphorylation patterns of p53 from normal and transformed mouse cells were quite similar. In contrast, p53 from normal and transformed rat cells exhibited dramatic quantitative and qualitative differences under these labeling conditions. The reverse was found after an 18-h label leading to steady-state phosphorylation of p53 in transformed cells: while p53 in transformed mouse cells revealed a marked quantitative increase in phosphorylation compared with p53 from normal cells, the corresponding patterns of p53 from normal and transformed rat cells were similar. Our data thus indicate species-specific differences in the phosphorylation of mouse and rat p53 in SV40-transformed cells, reflected by (i) different turnover rates at specific sites in mouse and rat p53 and (ii) phosphorylation of nonhomologous serine and threonine residues in rat p53, as revealed by indirect assignment of phosphorylation sites to the phosphopeptides of rat p53. Analyses of p53 from the SV40 tsA58 mutant-transformed F111 cell lines FR(tsA58)A (N type) and FR(tsA58)57 (A type) yielded no conclusive evidence for a direct correlation between phosphorylation of p53, the metabolic stabilization of p53, and expression of the transformed phenotype.
 ...
PMID:Species-specific phosphorylation of mouse and rat p53 in simian virus 40-transformed cells. 131 85

Lymphocyte activation requires signal transduction mediated by reversible phosphorylation. Changing profiles of phosphorylated intermediates relate to the progressive series of transduction pathways in cells moving from G0 to G1, and thereafter through the cell cycle. We have previously shown that transient inhibition of the serine/threonine protein phosphatases PP1 and PP2A by okadaic acid enhances early mitogenic stimulation. Thus target proteins of PP1/PP2A may be involved in regulation of early mitogenic signalling, with the phosphorylated form(s) being associated with signal enhancement. Later, pathways require dephosphorylation of these proteins, since continuous treatment with okadaic acid blocks lymphocyte progression through the cell cycle. Delayed addition of okadaic acid showed that this blockade occurs between 8 and 24 hr. Here we have furthered these observations to the level of gene induction by measuring messenger RNA (mRNA) levels for the following proteins: interleukin-2 (IL-2) and IL-2R alpha; p53, a tumour suppressor protein; the transcription factor krox-24; and two mediators of protein folding, namely cyclophilin and the heat-shock protein hsc70. An external standard was used to quantitate the mRNA levels per cell. We found that 24 hr exposure to okadaic acid has a general suppressive effect on concanavalin A (Con A)-stimulated gene induction. However, at 4 hr okadaic acid enhanced IL-2 mRNA levels induced by Con A. Moreover, in unstimulated lymphocytes, okadaic acid caused the induction of krox-24, indicating a role for PP1 and PP2A in the regulation of this gene in resting cells.
 ...
PMID:Inhibition of the serine/threonine protein phosphatases PP1 and PP2A in lymphocytes: effect on mRNA levels for interleukin-2, IL-2R alpha, krox-24, p53, hsc70 and cyclophilin. 132 40

Human cyclin B1-bound cdc2 kinase phosphorylated the threonine residue in the sequence -Thr-Pro-Lys-Lys-Ala- but hardly phosphorylated it in the sequence -Thr-Pro-Lys-Ala-Lys. The sequence -Thr-Pro-Ala-Pro-Lys-, as found in p53 protein, was also phosphorylated by this enzyme, but less efficiently than in the sequence described above. When the threonine residue in -Thr-Pro-Lys-Lys-Ala- was changed to a serine or a tyrosine residue, the enzyme phosphorylated the serine, but not the tyrosine residue. Changing the lysine next to the proline to alanine reduced its efficiency as a substrate. The peptide, Ala-Ala-Ala-Ala-Lys-Thr-Pro-Ala-Lys-Ala-Ala, containing the -Thr-Pro-Ala-Lys- sequence, but not the other lysine residues, was not used as a substrate by the kinase.
 ...
PMID:Preference of human cdc2 kinase for peptide substrate. 145 May 22

Alterations in the p53 tumor suppressor gene and Epstein-Barr virus status were investigated in 15 nasopharyngeal carcinoma (NPC) biopsies, 4 xenografts, and 2 cell lines from the Cantonese region of southern China. One other established NPC cell line obtained from a northern Chinese patient was also studied. Restriction fragment length polymorphism analysis revealed a loss of heterozygosity for chromosome 17p, where the p53 gene resides, in only one of 15 NPC biopsies. Polymerase chain reaction-single-stranded conformational polymorphism analysis and direct sequencing failed to detect sequence alterations in exons 5 through 8 of the p53 gene in the 15 tumors and in the 4 NPC xenografts, all of which tested positive for Epstein-Barr virus. In contrast, the 3 NPC cell lines were all negative for Epstein-Barr virus and contained G----C transversions in the p53 gene, with cell lines CNE-1 and CNE-2 harboring identical AGA (arginine) to ACA (threonine) changes at codon 280. These results suggest that p53 inactivation is not a necessary component of nasopharyngeal carcinogenesis in Cantonese but may be important in the establishment of cell lines derived from these tumors.
 ...
PMID:Absence of p53 gene mutations in primary nasopharyngeal carcinomas. 151 42

We generated a number of simian virus 40 (SV40) mutants with single amino acid substitutions in T antigen between residues 388 and 411. All but one mutant (398LV) replicated like wild-type SV40 and gave rise to normal-size plaques. Three different mutations at residue 402 (Asp to Glu, Asn, or His) totally prevented the formation of stable complexes with the cellular protein p53 in monkey cells but had no effect on virus replication. Only one other mutation in this region, involving residue 401 (Met to Thr), slightly inhibited the formation of T-monkey p53 complexes. The three mutant T antigens with substitutions at residue 402 also formed no stable complexes with human p53 but generated low levels of complexes with mouse p53. These results indicate that residue 402 is critical for binding to monkey and human p53 proteins and is important for binding to mouse p53. We suggest that it is one of several points of contact. In cells infected with any one of the three residue 402 mutant viruses. T antigen and p53 became increasingly phosphorylated, as they were in cells infected with wild-type virus. Our data therefore show that stable T-p53 complexes are not required for replication of SV40 in culture or for enhanced phosphorylation of either protein.
 ...
PMID:Stable T-p53 complexes are not required for replication of simian virus 40 in culture or for enhanced phosphorylation of T antigen and p53. 170 96

Inherited susceptibility to a wide variety of neoplasias (Li-Fraumeni syndrome), has been shown in studies of one cancer-prone family, to have an intriguing association with an aberrant c-raf-1 gene and inheritance of a radioresistant phenotype in their non-cancerous skin fibroblasts. This association together with observations that DNA topoisomerases, when defective, can introduce errors into DNA and that these enzymes are perturbed in vitro by serine/threonine kinases similar to raf encoded proteins, prompted investigation of DNA topoisomerase activity of the family's fibroblasts. Since radioresistance was transferred to murine cells (NIH-3T3) when the aberrant c-raf-1 gene from this family was transfected, we also examined transformants containing this and other oncogenes. V-raf/c-myc and EJ-ras transformants were examined, the former because the family's skin fibroblasts also have 3-8-fold elevated myc expression (not apparently relevant to radioresistance) and the latter because ras, like raf, conveys radioresistance. The family members' fibroblasts and the three transfected murine lines, showed a similar perturbation of a spermidine and ATP-dependent DNA catenation activity (typical of DNA topoisomerase II). There was a significant positive correlation (r = 0.93; P = 0.0026) between the degree of activation of topoisomerase II and one measure of radioresistance (the Dq value). Relaxation of DNA supercoiling (topoisomerase I activity and other DNA nicking enzymes) was not abnormal. Cytotoxicity assays and evaluation of the influence of topoisomerase II inhibitors on DNA/protein complex formation, corroborated the existence of a qualitative topoisomerase II defect in the family's cells and transfectants. Although the contention that the qualitative topoisomerase II abnormalities observed here may be associated with malfunction is highly speculative, these findings may be relevant to the mechanism of oncogenesis, not only in this family, but with raf and ras type oncogenes.
 ...
PMID:Aberrant DNA topoisomerase II activity, radioresistance and inherited susceptibility to cancer. 184 52

Synthetic peptide substrates for the cell division cycle regulated protein kinase, p34cdc2, have been developed and characterized. These peptides are based on the sequences of two known substrates of the enzyme, Simian Virus 40 Large T antigen and the human cellular recessive oncogene product, p53. The peptide sequences are H-A-D-A-Q-H-A-T-P-P-K-K-K-R-K-V-E-D-P-K-D-F-OH (T antigen) and H-K-R-A-L-P-N-N-T-S-S-S-P-Q-P-K-K-K-P-L-D-G-E-Y-NH2 (p53), and they have been employed in a rapid assay of phosphorylation in vitro. Both peptides show linear kinetics and an apparent Km of 74 and 120 microM, respectively, for the purified human enzyme. The T antigen peptide is specifically phosphorylated by p34cdc2 and not by seven other protein serine/threonine kinases, chosen because they represent major classes of such enzymes. The peptides have been used in whole cell lysates to detect protein kinase activity, and the cell cycle variation of this activity is comparable to that measured with specific immune and affinity complexes of p34cdc2. In addition, the peptide phosphorylation detected in mitotic cells is depleted by affinity adsorption of p34cdc2 using either antibodies to p34cdc2 or by immobilized p13, a p34cdc2-binding protein. Purification of peptide kinase activity from mitotic HeLa cells yields an enzyme indistinguishable from p34cdc2. These peptides should be useful in the investigation of p34cdc2 protein kinase and their regulation throughout the cell division cycle.
 ...
PMID:Characterization of synthetic peptide substrates for p34cdc2 protein kinase. 204 31

The full-length provirus of human T-cell leukemia virus type I (HTLV-I) was isolated from MT-2, a lymphoid cell line producing HTLV-I. In transfected cells, structural proteins of HTLV-I, the gag and env products, were formed and processed in the same manner as observed in MT-2 cells. The nucleotide sequence was determined for a region between the gag and pol genes of the proviral DNA clone containing an open-reading frame. The deduced amino acid sequences show that this open-reading frame encodes a putative HTLV-I protease. The protease gene (pro) of HTLV-I was investigated using a vaccinia virus expression vector. Processing of 53k gag precursor polyprotein into mature p19, p24, and p15 gag structural proteins was detectable with a recombinant plasmid harboring the entire gag- and protease-coding sequence. We demonstrated that the protease processed the gag precursor polyprotein in a trans-action. A change in the sequence Asp(64)-Thr-Gly, the catalytic core sequence among aspartyl proteases, to Gly-Thr-Gly was shown to abolish correct processing, suggesting that HTLV-I protease may belong to the aspartyl protease group. The 76k gag-pro precursor polyprotein was identified, implying that a cis-acting function of HTLV-I protease may be necessary to trigger the initial cleavage event for its own release from a precursor protein, followed by the release of p53 gag precursor protein. The p53 gag precursor protein is then processed by the trans-action of the released protease to form p19, p24, and p15.
 ...
PMID:Identification of HTLV-I gag protease and its sequential processing of the gag gene product. 266 87

We have examined the large T encoded by an SV40 mutant, d10, which fails to localize to the nucleus. The DNA sequence of the mutant predicts the alteration of Lys 128----Thr within the sequence 127 Lys Lys Lys Arg Lys 131 of large T. The results show that d10 large T is capable of binding to SV40 DNA, to cellular DNA and to the cellular phosphoprotein p53 as well as wild-type large T. These data suggest that the cytoplasmic location of d10 large T is not due to an inability of the protein to be retained within the nucleus, but argues instead that the protein fails to reach the nucleus because it contains a defective nuclear location signal.
 ...
PMID:The abnormal location of cytoplasmic SV40 large T is not caused by failure to bind to DNA or to p53. 300 45


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