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Biomedical subjects

P Whyte

Publications and source records attributed to P Whyte.

At least 55 records · Page 3Linked to original sources
PubMed1992

Dephosphorylation of the retinoblastoma protein during differentiation of HL60 cells.

Immunoprecipitated retinoblastoma protein from HL60 cells migrated as a series of bands during electrophoresis. The heterogeneity appeared to be generated by phosphorylation of the retinoblastoma protein. Treatment of the cells with the phorbol ester, tetradecanoyl phorbol acetate (TPA), resulted in both a loss of the heterogeneity of the pRB species and a significant decrease in the level of pRB phosphorylation. These changes accompanied differentiation of the HL60 cells into macrophages. Treatment of the cells with dibutyryl cAMP also resulted in dephosphorylation of pRB as well as cell cycle arrest, although no recognizable differentiation occurred. These results are consistent with a model in which TPA and dibutyryl cAMP dependent pathways can activate pRB by altering its phosphorylation.

Bucladesine↗
PubMed1991

Handling the pressure on an offshore rig.

The chief instigator of offshore stress is time which in oil parlance is money, writes Patrick Whyte, an offshore medical officer. He explains that medical personnel by showing that they practice a healthy lifestyle on the offshore oil rigs can set a practical example of coping with the stressful conditions.

Adaptation, Psychological↗
PubMed1991

Human cyclin A and the retinoblastoma protein interact with similar but distinguishable sequences in the adenovirus E1A gene product.

The adenovirus early region 1A (E1A) proteins associate with several cellular proteins in adenovirus infected or transformed cells. Recently, two of the cellular proteins that bind to E1A encoded proteins have been identified. p105 has been shown to be the product of the retinoblastoma tumor suppressing gene. p60 has been shown to be a human cyclin A. Previously studies have shown that E1A protein sequences encoded by conserved domains 1 and 2 are required for interactions with the retinoblastoma protein (pRB). We have demonstrated here that amino acids 30 to 60 and 121 to 127 within the E1A proteins are required for interaction with p60/cyclin A. These are the same sites within conserved domains 1 and 2 that are required for E1A protein association with pRB. However, the association of p60/cyclin A does not appear to require pRB. We also demonstrate that another cellular protein, 130K, interacts with E1A at essentially the same sites. It is interesting that mutations in these regions destroy the ability of E1A to function as an oncogene, thereby raising the possibility that interaction with several different cellular proteins may be needed for transformation by E1A.

Adenoviridae↗
PubMed1990

Cellular proteins that are targets for transformation by DNA tumour viruses.

Small DNA tumour viruses produce proteins that redirect cellular gene expression and growth control. The E1A polypeptides of adenovirus perform the functions of transcriptional activation and cellular transformation. These two functions are carried out by different domains within the E1A protein. The E1A protein associates with several cellular proteins, including the product of the retinoblastoma gene, pRb-1. Mutational analysis correlates transformation with the sites required for binding pRb and two other cellular proteins, p107 and a 300 kDa polypeptide. This correlation suggests that these proteins are targets for E1A-mediated transformation. Transforming proteins from other small DNA tumour viruses interact with pRb, raising the possibility that a common event in viral transformation is the inactivation of proteins that inhibit cellular proliferation. The role of the E1A-associated 60 kDa protein, p60, in transformation is being investigated. In the absence of E1A, p60 binds to the human homologue of the Schizosaccharomyces pombe cdc2 gene product, p34, to form a complex that has kinase activity that oscillates during the cell cycle. Ongoing studies of the effect of adenovirus infection, and specifically E1A expression, on this cellular kinase may provide clues to how E1A overcomes cell cycle controls and transforms cells.

Adenoviridae↗
PubMed1989

A 60 kd cdc2-associated polypeptide complexes with the E1A proteins in adenovirus-infected cells.

p60 is a cellular protein that binds to the adenovirus E1A protein complex in virally infected or transformed human cells. In both infected and uninfected cells, p60 was found in a complex with the cdc2 protein kinase. Immune complexes containing p60 and cdc2 display a cell cycle-dependent histone H1 kinase activity that is most active in interphase. The previously described cdc2-p62/cyclin complex also acts as a histone H1 kinase but is maximally active in mitotic metaphase. The shift in the timing of activation of different cdc2-containing complexes suggests that each might play a distinct role in regulation of the cell cycle.

Adenovirus Early Proteins↗
PubMed1989

The cellular 107K protein that binds to adenovirus E1A also associates with the large T antigens of SV40 and JC virus.

The association between the retinoblastoma protein (p105-RB) and either the large T antigen of SV40 or the E1A proteins of adenovirus is thought to be an important step in transformation by these viral oncogenes. E1A and large T antigen share a small region of amino acid homology that is necessary for high affinity binding with p105-RB. Mutations of this homology region were shown to reduce drastically the frequency of transformation mediated by the E1A or large T oncogenes. Previously, this small region in E1A was shown to be sufficient for interaction with a second cellular protein of 107,000 daltons (107K). Here we show that in human cells, the large T antigens of SV40 or JC virus also form complexes with 107K. Demonstration of complexes between 107K and the large T antigens of SV40 and JC virus suggests that these associations may represent another component of a common mechanism for transformation between adenoviruses and polyoma viruses.

Adenovirus Early Proteins↗
PubMed1989

Point mutational inactivation of the retinoblastoma antioncogene.

The retinoblastoma (Rb) antioncogene encodes a nuclear phosphoprotein, p105-Rb, that forms protein complexes with the adenovirus E1A and SV40 large T oncoproteins. A novel, aberrant Rb protein detected in J82 bladder carcinoma cells was not able to form a complex with E1A and was less stable than p105-Rb. By means of a rapid method for the detection of mutations in Rb mRNA, this defective Rb protein was observed to result from a single point mutation within a splice acceptor sequence in J82 genomic DNA. This mutation eliminates a single exon and 35 amino acids from its encoded protein product.

Adenovirus Early Proteins↗
PubMed1989

Cellular targets for transformation by the adenovirus E1A proteins.

Three cellular proteins, including species of 300,000 daltons and 107,000 daltons as well as p105-RB, the product of the retinoblastoma susceptibility gene, stably interact with the adenovirus E1A proteins. To help determine the functional basis of these interactions, the regions of E1A that participate in these interactions were mapped using a series of deletion mutants. The 300,000 dalton and the 107,000 dalton proteins interacted with sequences within amino acids 1 to 76 and 121 to 127, respectively. Interaction with the third cellular protein, p105-RB, required the presence of sequences from two noncontiguous regions of the E1A polypeptide chain, amino acids 30 to 60 and 121 to 127. The regions of E1A that are required for these interactions coincided precisely with the regions of E1A that are required for its transforming function. These results suggest that the interactions with these cellular proteins are fundamental to the transforming activity of E1A.

Adenovirus Early Proteins↗
PubMed1989

Cellular proteins that are targetted by DNA tumor viruses for transformation.

Tumor suppressor genes are genetic loci whose loss is associated with tumor development. Because the inactivation of these genes is a key feature in the genesis of certain tumors, it has been postulated that the protein products of tumor suppressor genes function in the negative regulation of cell proliferation. Tumor suppressor genes have been identified by genetic analysis either as loci associated with an inherited predisposition to certain tumors or by mapping studies that demonstrate allelic loss (reduction to homozygosity or loss of heterozygosity) during tumor development. The retinoblastoma gene, RB-1, was originally identified and cloned through its association with childhood retinoblastoma and is one of the best studied examples of the tumor suppressor genes. It has been shown that RB protein is also a key target for transformation by the oncogenes of several small DNA tumor viruses. The E1A proteins of adenovirus, the large T antigens of polyomaviruses, and E7 proteins of papillomaviruses all bind to pRB. Genetic studies of all three viruses have shown that any mutation that destroys binding to pRB also destroys the ability of these proteins to transform cells, suggesting that interaction with the RB gene product is a key event in viral transformation. In addition to interacting with pRB, the adenovirus E1A proteins and the polyomavirus large T antigens also bind to other cellular proteins. One of these, a protein with a molecular weight 0f 107,000 daltons, 107K, binds to E1A and large T at the same amino acid region as pRB, suggesting that the 107K and pRB proteins may have structural similarities.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Association between an oncogene and an anti-oncogene: the adenovirus E1A proteins bind to the retinoblastoma gene product.

One of the cellular targets implicated in the process of transformation by the adenovirus E1A proteins is a 105K cellular protein. Previously, this protein had been shown to form stable protein/protein complexes with the E1A polypeptides but its identity was unknown. Here, we demonstrate that it is the product of the retinoblastoma gene. The interaction between E1A and the retinoblastoma gene product is the first demonstration of a physical link between an oncogene and an anti-oncogene.

Adenovirus Early Proteins↗
PubMed1988

Towards a live oral vaccine against enterotoxigenic Escherichia coli of swine.

A live oral vaccine has been developed against scouring induced in piglets by enterotoxigenic Escherichia coli (ETEC). An attenuated strain of Salmonella typhimurium, G30, has been used as a vector for plasmids encoding the production of the fimbrial colonization factors of porcine ETEC. Initial studies with clones expressing K88 or K99 fimbriae have shown them to be well tolerated when administered orally in very high doses. The clones elicited serum, colostral and milk antibodies to the fimbrial antigens, and a challenge trial indicated that such responses were sufficient to ensure the passive transfer of protective immunity to suckling piglets. The possible advantages of this approach are discussed.

Administration, Oral↗
PubMed1988

Two regions of the adenovirus early region 1A proteins are required for transformation.

Regions of the adenovirus type 5 early region 1A (E1A) proteins that are required for transformation were defined by using a series of deletion mutants. Deletion mutations collectively spanning the entire protein-coding region of E1A were constructed and assayed for their ability to cooperate with an activated ras oncogene to induce transformation in primary baby rat kidney cells. Two regions of E1A (amino acids 1 to 85 and 121 to 127) were found to be essential for transformation. Deletion of all or part of the region from amino acids 121 to 127 resulted in a total loss of transforming ability. An adjacent stretch of amino acids (residues 128 to 139), largely consisting of acidic residues, was found to be dispensable for transformation but appeared to influence the efficiency of transformation. Amino acids 1 to 85 made up a second region of the E1A protein that was essential for transformation. Deletion of all or part of this region resulted in a loss of the transforming activity. Even a mutation resulting in a single amino acid change at position 2 of the polypeptide chain was sufficient to eliminate transformation. Deletion of amino acids 86 to 120 or 128 to 289 did not eliminate transformation, although some mutations in these regions had lowered efficiencies of transformation. Foci induced by transformation-competent mutants could be expanded into cell lines that retained their transformed morphology and constitutively expressed the mutant E1A proteins.

Adenovirus Early Proteins↗
PubMed1988

Growth factor induction by the adenovirus type 5 E1A 12S protein is required for immortalization of primary epithelial cells.

The 12S protein encoded by the adenovirus E1A region induces cellular DNA synthesis in and proliferation and immortalization of primary rat epithelial cells in the presence or absence of serum. It also induces the production of a growth factor(s) that stimulates epithelial cell proliferation. We have undertaken a mutational analysis of the 12S gene to determine the sequences required for these functions. We found that a region near the C-terminus of the 12S protein was required for growth factor induction. No activities have been defined previously for this region. Furthermore, we show that growth factor production was necessary for epithelial cells to survive past their normal life span in culture and to become immortalized. The ability to induce growth factor production required prior expression of E1A activities encoded by the N-terminus of the 12S protein, including activation of quiescent cells into the cell cycle, and an unknown activity that required expression of the first 13 amino acids of the gene. In addition, examination of the subcellular localization of mutant 12S polypeptides suggested new regions that affect the nuclear localization of E1A proteins.

Adenovirus Early Proteins↗
PubMed1986

Association of adenovirus early-region 1A proteins with cellular polypeptides.

Extracts from adenovirus-transformed human 293 cells were immunoprecipitated with monoclonal antibodies specific for the early-region 1A (E1A) proteins. In addition to the E1A polypeptides, these antibodies precipitated a series of proteins with relative molecular weights of 28,000, 40,000, 50,000, 60,000, 80,000, 90,000, 110,000, 130,000, and 300,000. The two most abundant of these polypeptides are the 110,000-molecular-weight protein (110K protein) and 300K protein. Three experimental approaches have suggested that the 110K and 300K polypeptides are precipitated because they form stable complexes with the E1A proteins. The 110K and 300K polypeptides do not share epitopes with the E1A proteins, they copurify with a subset of the E1A proteins, and they bind to the E1A proteins following mixing in vitro. The 110K and 300K polypeptides are not adenoviral proteins, but are encoded by cellular DNA. Both the 12S and the 13S E1A proteins bind to the 110K and 300K species, and these complexes are found in adenovirus-transformed and -infected cells.

Adenovirus Early Proteins↗
PubMed1985

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Accidents, Occupational↗