Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have examined the effects of the E1a products of adenovirus types 5 and 12 on the expression of polyomavirus early and late promoters. In cotransfection experiments in HeLa cells, plasmids expressing the E1a region of adenovirus type 5 or 12 repressed both the early and late promoters of polyomavirus, and deletion analysis indicates that the polyomavirus enhancers were the target of the E1a repression. With mutants lacking enhancer sequences, the polyomavirus early promoter but not the late promoter was trans-activated by E1a. Chimeric mutant plasmids with deletions in the regulatory region that contained either the A enhancer or the B enhancer were repressed to the same extent, indicating that E1a can repress both elements. Polyomavirus variant plasmids with rearrangements in the regulatory region conferring activity in embryonal carcinoma stem cells were repressed by E1a as was the wild type, suggesting that the repressor function is quite general. We discuss a model in which the influence of E1a on the transcriptional activity of a gene is the sum of positive and negative effects on promoter and enhancer elements and discuss possible mechanisms of negative regulation of enhancer function.
Mol Cell Biol 1986 Nov
PMID:Adenovirus E1a proteins repress expression from polyomavirus early and late promoters. 302 25

The polyomavirus enhancer is required in cis for high-level expression of the viral early region and for replication of the viral genome. We introduced multiple mutations in the enhancer which reduced transcription and DNA replication. Polyomaviruses with these mutant enhancers formed very small plaques in whole mouse embryo cells. Revertants of the viral mutants were isolated and characterized. Reversion occurred by any of the following events: restoration of guanosines at nucleotide (nt) 5134 and nt 5140 within the adenovirus 5 E1A enhancer core AGGAAGTGACT; acquisition of an A----G mutation at nt 5258, which is the same mutation that enables polyomavirus to grow in embryonal carcinoma F9 cells; duplication of mutated sequences between nt 5146 and 5292 (including sequences homologous with immunoglobulin G, simian virus 40, and bovine papillomavirus enhancer elements). Reversion restored both the replicative and transcriptional functions of the viruses. Revertants that acquired the F9 mutation at nt 5258 grew at least 20-fold better than the original mutant in whole mouse embryo cells, but replicated only marginally better than the original mutant in 3T6 cells. Viruses with a reversion of the mutation at nt 5140 replicated equally well in both types of cells. Since individual nucleotides in the polyomavirus enhancer simultaneously altered DNA replication and transcription in specific cell types, it is likely that these processes rely upon a common element, such as an enhancer-binding protein.
Mol Cell Biol 1987 May
PMID:Nucleotides in the polyomavirus enhancer that control viral transcription and DNA replication. 303 32

The host restriction imposed on polyoma virus by embryonal carcinoma cells can be circumvented by mutations in the enhancer region of the viral genome. In addition, expression of the early viral genes can be induced by differentiating cells transfected with purified viral DNA. Although no host-range mutants of SV40 have been isolated, expression of T antigen from episomal genomes can be induced by differentiating the embryonal carcinoma cells transfected with microgram quantities of DNA. Further, transient expression of T antigen can be observed in the embryonal carcinoma cells following transfection with large amounts of viral DNA. In addition, replication of the A2 strain of polyoma in F9 cells is enhancer dependent but the SV40 enhancer can functionally substitute for the polyoma enhancer. The F9 host-range mutant TT340 contains five tandem repeats of the region surrounding the origin of replication, and it requires T antigen for replication. The parental strain (Toronto) of the mutant is able to replicate at low levels in a T antigen-dependent manner in F9 cells. This strain also has an unselected host range for PCC4 cells and the mutation in TT340 required for growth on F9 cells does not alter this inherent host range.
Exp Mol Pathol 1987 Aug
PMID:Further characterization of the interaction of polyoma virus and simian virus 40 with embryonal carcinoma cells. 303 93

A mutant polyoma virus (TT340), which replicates in F9 embryonal carcinoma (EC) cells and contains 2500 base pairs (bp) of additional DNA located in the early noncoding region of the genome, was analyzed to determined the DNA origin of the mutant insertion. Two fragments, representing repeated units of the 2500-bp insert, were isolated from TT340, labeled, and hybridized to the parental wild-type viral DNA. A BglI 500-bp unit, of which there are approximately five copies within the 2500-bp insert, contains sequences homologous to regions on the early and late side of the viral origin of replication. A HpaII 400-bp repeated fragment shows homology to sequences on the early side with little hybridization to the late side. Removal of the 2500-bp insert results in the loss of infectivity on F9 EC cells but not on 3T6 or mouse embryo fibroblasts. Insertion of the BglI 500-bp repeat element into wild-type DNA at the BglI site allows replication of the constructed virus in F9 cells. The mutant virions were tumorigenic in newborn Syrian hamsters and the morphology of the virus was that of wild-type as assayed by electron microscopy.
Exp Mol Pathol 1987 Aug
PMID:Characterization of a mutant polyoma that expresses in F9 embryonal carcinoma cells: morphology, tumorigenicity, and restriction enzyme analysis. 303 94

Chromosomal loci that are specifically active in embryonal carcinoma stem cells were cloned from the mouse genome by functional selection. P19 cells, a pluripotent embryonal carcinoma cell line, were transfected with an enhancer trap (a plasmid containing an enhancerless inactive neo gene), and NEO+ transformants were isolated. All of the NEO+ cell lines retained pluripotency and expressed the neo gene. When the cells were induced to differentiate, most of the cell lines continued to express the neo gene, while the neo gene in some cell lines became repressed. From the latter group of cell lines, we have cloned the integrated neo gene plus the flanking cellular DNA sequences. Three of the six cloned DNAs possessed a high NEO+-transforming activity in undifferentiated P19 cells. Among these three, two (015 and 052) were inactive in differentiated P19 cells and NIH 3T3 cells, while the remaining one was active in these differentiated cells. Deletion analysis suggested that both 015 and 052 contain two regulatory elements (promoter and enhancer) of cellular DNA origin. The putative enhancer and promoter are separated by at least 6 kilobases in 015 and 1 kilobase in 052. Therefore, 015 and 052 cloned fragments contain regulatory DNA elements that are specifically active in the embryonal carcinoma stem cells.
Mol Cell Biol 1988 Aug
PMID:Functional cloning of mouse chromosomal loci specifically active in embryonal carcinoma stem cells. 321 Nov 42

P19 embryonal carcinoma (EC) cells are multipotential stem cells which can be induced to differentiate in vitro into a variety of cell types, including cardiac muscle cells. A cloned human cardiac actin (CH-actin) gene was transfected into P19 cells, and stable transformants were isolated. Low levels of CH-actin mRNA were present in transformed EC cells, but a marked increase in the level of CH-actin mRNA was found as these cells differentiated into cardiac muscle. The accumulation of CH-actin mRNA paralleled that of the endogenous mouse cardiac actin mRNA. A chimeric gene, which consisted of the CH-actin promoter linked to the herpes simplex virus thymidine kinase coding region, was constructed and transfected into P19 cells. In these transformants, the thymidine kinase protein was located almost exclusively in cardiac muscle cells and was generally not detectable in EC or other nonmuscle cells. These results suggest that the transfected CH-actin promoter functions in the appropriate developmental and tissue-specific manner during the differentiation of multipotential EC cells in culture.
Mol Cell Biol 1988 Jan
PMID:Regulated expression of a transfected human cardiac actin gene during differentiation of multipotential murine embryonal carcinoma cells. 327 77

Transcription of mouse major histocompatibility complex class I genes is controlled by the conserved class I regulatory element (CRE) in the 5' flanking region. The CRE, approximately 40 base pairs long, acts as a negative control element in undifferentiated F9 embryonal carcinoma cells which do not express the major histocompatibility complex genes. The same element, however, acts as a positive control element in cells expressing the genes at high levels. To investigate the molecular basis of the regulatory role of the CRE, we studied the binding of nuclear proteins to the CRE of the H-2Ld gene by gel mobility shift and methylation interference experiments. Nuclear extracts from L fibroblasts and LH8 T lymphocytes revealed three distinct factors that bind discrete sequences within the CRE. The three sequences correspond to the inverted and direct repeats within the CRE. In contrast, F9 extracts exhibited factor binding to only two of the three sequences and lack a major factor detected in the above two cell types. Protein-binding sites within each of the three sequences were identified by methylation interference experiments. These data were in full agreement with results obtained by a competition assay performed with a series of mutant oligonucleotides containing a few nucleotide substitutions in each of the three regions. The results illustrate complex DNA-protein interactions in which several independent proteins bind to overlapping sequences in the CRE in a cell type-specific fashion.
Mol Cell Biol 1987 Dec
PMID:Binding of multiple nuclear factors to the 5' upstream regulatory element of the murine major histocompatibility class I gene. 350 25

Binding sites for six distinct nuclear factors on the 75-base-pair repeat of the Moloney murine leukemia virus enhancer have been identified by an electrophoretic mobility shift assay combined with methylation interference. Three of these factors, found in WEHI 231 nuclear extracts, which we have named LVa, LVb, and LVc (for leukemia virus factors a, b, and c) have not been previously identified. Nuclear factors that bind to the conserved simian virus 40 corelike motif, the NF-1 motif, and the glucocorticoid response element were also detected. Testing of multiple cell lines showed that most factors appeared ubiquitous, except that the NF-1 binding factor was found neither in nuclear extracts from MEL cells nor in the embryonal carcinoma cell lines PCC4 and F9, and core-binding factor was relatively depleted from MEL and F9 nuclear extracts.
Mol Cell Biol 1987 Mar
PMID:Six distinct nuclear factors interact with the 75-base-pair repeat of the Moloney murine leukemia virus enhancer. 356 10

Embryonal carcinoma (EC) cells are nonpermissive for retrovirus replication. Restriction of retroviral expression in EC cells was studied by using DNA transfection techniques. To investigate the activity of the Moloney murine leukemia virus (M-MuLV)enhancer and promoter sequences, the M-MuLV long terminal repeat and the defined long terminal repeat deletions were linked to neo structural gene sequences that encode resistance to the neomycin analog G418. Transient expression data and drug resistance frequencies support the findings that the M-MuLV enhancer is not active in EC cells but that promoter sequences are functional. In addition, a proviral DNA fragment that encodes the leader RNA sequence of a M-MuLV recombinant retrovirus was found to restrict expression specifically in EC cells. Deletion analysis of the leader fragment localized the inhibitory sequences to a region that spans the M-MuLV tRNA primer binding site. It is not known whether restriction occurs at a transcriptional or posttranscriptional level, but steady-state RNA levels in transient expression assays were significantly reduced.
Mol Cell Biol 1987 Oct
PMID:Proviral sequences that restrict retroviral expression in mouse embryonal carcinoma cells. 368 98

We transfected the human EJ bladder carcinoma oncogene (Ha-rasEJ-1) into multipotential embryonal carcinoma cell line P19. The transgenic P19(ras+) cells expressed high levels of both the mRNA and the p21EJ protein derived from the oncogene. When cultured in the presence of retinoic acid, P19(ras+) cells differentiated and developed into the same spectrum of differentiated cell types as the parental P19 cells (namely, neurons, astrocytes, and fibroblast-like cells). Thus, it seems unlikely that the Ha-ras-1 proto-oncogene product plays a role in initiation of differentiation or in the choice of differentiated cell lineage. Most of the P19(ras+)-derived differentiated cells contained relatively low levels of p21EJ and were nontransformed, whereas certain cells with fibroblast-like morphology continued to express the Ha-rasEJ-1 gene at high levels and were transformed (i.e., immortal and anchorage independent). Fibroblasts derived from P19 cells did not become transformed following transfection of the Ha-rasEJ-1 oncogene, suggesting that transformation of the fibroblast cells only occurred if the oncogene was present and expressed during the early stages of the developmental lineage.
Mol Cell Biol 1986 Feb
PMID:Lineage-specific transformation after differentiation of multipotential murine stem cells containing a human oncogene. 378 55


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