Biomedical subjects

D C Rio

Publications and source records attributed to D C Rio.

56 records · Page 4Linked to original sources

PubMed1981

SV40 gene expression is modulated by the cooperative binding of T antigen to DNA.

We analyzed the DNA binding properties of wild-type simian virus 40 large T antigen and found that the protein binds cooperatively to three tandem sites at a regulatory region of SV40 DNA. One consequence of this T antigen:DNA interaction is the specific repression of SV40 early RNA synthesis in vitro. We mapped a region of 85 base pairs that is necessary and sufficient to initiate early SV40 transcription in vitro. This promoter region lies directly adjacent to the third T antigen binding site but does not include that "TATA" sequence. To determine how T antigen interacts with its binding sites to repress RNA synthesis, we analyzed transcription directed by a variety of wild-type, mutant and hybrid template DNAs. Our findings suggest that the cooperative binding of T antigen to its sites is directly responsible for inhibiting the initiation, rather than blocking elongation, of early RNA synthesis. A model is presented to explain the role of T antigen binding in the regulation of viral transcription and DNA replication during SV40 lytic infection.

Antigens, Neoplasm↗

PubMed1979

Localization of transcribed regions on extrachromosomal ribosomal RNA genes of Tetrahymena thermophila by R-loop mapping.

R-loop hybridization and electron microscopy were used to map the RNA transcription products of the extrachromosomal rRNA genes of Tetrahymena thermophila. The mature 17S and 26S rRNAs and the nuclear 35S pre-rRNA and pre-26S rRNA were located with a precision of approximately 100 base pairs. A 370-base pair intervening sequence was found in the 26S coding region. It has the same size and relative location as that found in Tetrahymena pigmentosa [Wild, M.A. & Gall, J.G. (1979) Cell 16, 565-573]. One class of R-loop structures formed by nuclear pre-rRNA provided preliminary evidence for a primary transcript that contains the intervening sequence. The results suggested a processing scheme in which splicing of the intervening sequences is followed by a series of strand cleavages to give the mature 17S and 26S rRNAs. Analysis of the data also showed that RNA . DNA and DNA . DNA duplexes, when mounted for electron microscopy by the R-loop procedure, have the same length per base pair within 4%.

Animals↗