Search PubMed⌕ Search

Biomedical subjects

P Hearing

Publications and source records attributed to P Hearing.

46 records · Page 3Linked to original sources
PubMed1987

Identification of a repeated sequence element required for efficient encapsidation of the adenovirus type 5 chromosome.

Adenovirus type 5 deletion mutants that lack portions of their cis-acting DNA encapsidation signal synthesized nearly normal levels of viral DNA and late polypeptides but failed to efficiently package the DNA into virus particles. A series of mutant viruses carrying small deletions were produced and used to identify a repeated element (AGTAAATTTGGGC and AGTAAGATTTGGCC) as a key component of the packaging signal. One copy of the repeat was sufficient to signal efficient packaging. The packaging domain could function near either end of the viral chromosome but was no longer active when moved several hundred base pairs toward the interior of the DNA molecule.

Adenoviruses, Human↗
PubMed1986

The adenovirus type 5 E1A enhancer contains two functionally distinct domains: one is specific for E1A and the other modulates all early units in cis.

The adenovirus type 5 genome contains two distinct enhancer elements located at the left end of the viral chromosome. The first element is repeated and specifically regulates region E1A transcription within infected cells. One copy of this element is sufficient to fully activate E1A transcription in vivo. The second element is located between these repeated sequences and regulates transcription in cis of all early regions on the chromosome. These enhancer elements function independently of each other, and neither element is required for efficient viral DNA replication. Since mutations within the two E1A enhancer components generate different physiological responses, transcriptional enhancement can be achieved through multiple mechanisms.

Adenovirus Early Proteins↗
PubMed1986

Interaction of a nuclear factor with the polyomavirus enhancer region.

We have identified a factor present in nuclear extracts of undifferentiated F9 murine embryonal carcinoma cells that specifically interacts with the polyomavirus enhancer region. Nuclease "footprint" analysis was used to define the binding site that corresponds precisely to the boundaries of polyoma enhancer element C defined by Veldman et al. [Veldman, G. M., Lupton, S. & Kamen, R. (1985) Mol. Cell. Biol. 5, 649-658] that is required as an enhancer for efficient viral DNA replication and early and late region transcription. The region of nuclease protection contains a 6-base-pair inverted repeat, separated by 3 base pairs, and symmetrical flanking DNase I hypersensitive cleavage sites, suggesting that this factor may bind as a dimer. A cloned 29-base-pair polyoma DNA fragment contains an intact binding domain. Similar levels of binding activity were found in nuclear extracts prepared from differentiated murine F9 cells, as well as murine L cells and human HeLa cells. The factor has been termed "EF-C" for enhancer binding factor to polyoma element C.

Cell Line↗
PubMed1985

Sequence-independent autoregulation of the adenovirus type 5 E1A transcription unit.

The adenovirus E1A gene is known to be autoregulated at the level of transcription. Autoregulation was found to be mediated by products of the E1A 13S mRNA, which induced a fivefold increase in E1A transcription rate. Deletion analysis suggested that the autoregulation did not require any specific sequence in the E1A transcriptional control region. This conclusion was reinforced by the demonstration that a cellular alpha-globin gene substituted for the E1A gene on the adenovirus chromosome was also positively regulated by E1A gene products.

Adenovirus Early Proteins↗
PubMed1984

Adenovirus early region 1B 58,000-dalton tumor antigen is physically associated with an early region 4 25,000-dalton protein in productively infected cells.

In soluble protein extracts obtained from adenovirus productively infected cells, monoclonal antibodies directed against the early region 1B 58,000-dalton (E1B-58K) protein immunoprecipitated, in addition to this protein, a polypeptide of 25,000 molecular weight. An analysis of tryptic peptides derived from this 25K protein demonstrated that it was unrelated to the E1B-58K protein. The tryptic peptide maps of the 25K protein produced in adenovirus 5 (Ad5)-infected HeLa cells and BHK cells were identical, whereas Ad3-infected HeLa cells produced a different 25K protein. The viral origin of this 25K protein was confirmed by an amino acid sequence determination of five methionine residues in two Ad2 tryptic peptides derived from the 25K protein. The positions of these methionine residues in the 25K protein were compared with the nucleotide sequence of Ad2 and uniquely mapped the gene for this protein to early region 4, subregion 6 of the viral genome. A mutant of Ad5 was obtained (Ad5 dl342) which failed to produce detectable levels of the E1B-58K protein. In HeLa cells infected with this mutant, monoclonal antibodies directed against the E1B-58K protein failed to detect the associated 25K protein. In 293 cells infected with Ad5 dl342, which contain an E1B-58K protein encoded by the integrated adenovirus genome, the mutant produced an E4-25K protein which associated with the E1B-58K protein derived from the integrated genome. Extracts of labeled Ad5 dl342-infected HeLa cells (E1B-58K-) were mixed in vitro with extracts of unlabeled Ad5 wild type-infected HeLa cells or 293 cells (E1B-58K+). When the mixed extracts were incubated with the E1B-58K monoclonal antibody, a labeled E4-25K protein was coimmunoprecipitated. When extracts of Ad5 dl342-infected HeLa cells and uninfected HeLa cells (both E1B-58K-) were mixed, the E1B-58K monoclonal antibody failed to immunoselect the E4-25K protein. These data provide evidence that the E1B-58K antigen is physically associated with an E4-25K protein in productively infected cells. This is the same E1B-58K protein that was previously shown to be associated with the cellular p53 antigen in adenovirus-transformed cells.

Adenoviridae↗
PubMed1983

Functional analysis of the nucleotide sequence surrounding the cap site for adenovirus type 5 region E1A messenger RNAs.

We have constructed a set of small, dispersed deletion mutations in the sequences surrounding the cap site of the adenovirus type 5 region E1A transcription unit. The effects of the mutations on E1A transcription were studied in vitro using a HeLa cell-free extract, and in vivo by reconstructing the mutations back into intact viral chromosomes and analyzing E1A messenger RNAs synthesized after infection of HeLa cells. The sequence between -35 and +20 (relative to the cap site at +1) was important for efficient E1A transcription and cap site selection in vitro. This region includes the "TATA" homology, which appeared essential for transcription. Sequences upstream of -35 were dispensable for transcription in vitro. Different results were found upon analysis of the same set of deletions in vivo. None of the mutations affected the steady-state levels of cytoplasmic, E1A-specific mRNAs found in infected HeLa cells by more than twofold. Deletions of the TATA homology, however, generated E1A mRNAs with heterogeneous 5' ends, and deletions downstream of the homology displaced the 5' end of mRNAs by about the size of the deletion.

Adenoviridae↗
PubMed1983

The adenovirus type 5 E1A transcriptional control region contains a duplicated enhancer element.

The adenovirus type 5 E1A transcriptional control region contains an element with enhancer properties located between -141 and -305 relative to the E1A cap site at +1. The enhancer element is located at or very close to a sequence required in cis for packaging of viral DNA. Deletion of the element reduces both the rate of transcription and steady-state levels of E1A mRNAs in virus-infected cells. Such deletions also cause a modest reduction in activity of the E1B transcription unit, which is located immediately downstream of the E1A unit. The enhancer element includes repeated core sequences. Function is retained when the element is moved to the 3' side of the E1A gene in either possible orientation, and the E1A enhancer functions in cis to enhance transformation by the herpesvirus thymidine kinase gene in both mouse and human cells.

Adenoviruses, Human↗
PubMed1979

Cellular proteins associated with simian virus 40 early gene products in newly infected cells.

Immunoprecipitates of extracts of simian virus 40-infected permissive monkey kidney cells contained two proteins with molecular weights of 56,000 and 32,000 (52K and 32K) in addition to the known viral early gene products. Immunoprecipitates of cells infected with the 0.54-0.59 deletion mutants that lack the viral 17K gene product did not contain thhe 56K and 32K proteins. The additional proteins appeared in immunoprecipitates of deletion mutant extracts if unlabeled extracts of wild-type-infected cells were added before addition of antiserum. The proteins can also be identified in uninfected cells by co-precipitation with unlabeled viral proteins. Thus, it appears that the 56K and 32K proteins are cellular products that associate with the viral proteins, the 17K in particular, and are indirectly immunoprecipitated by anti-tumor serum.

Animals↗