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R Swanstrom

Publications and source records attributed to R Swanstrom.

77 records · Page 5Linked to original sources
PubMed1980

The nucleotide sequence of an untranslated but conserved domain at the 3' end of the avian sarcoma virus genome.

The genomes of numerous avian retroviruses contain at their 3' termini a conserved domain denoted "c". The precise boundaries and function of "c" have been enigmas. In an effort to resolve these issues, we determined the sequence of over 900 nucleotides at the 3' end of the genome of the Schmidt-Ruppin subgroup A strain of avian sarcoma virus (ASV). We obtained the sequence from a suitable fragment of ASV DNA that had cloned into the single-stranded DNA phage M13mp2. Computer-assisted analysis of the sequence revealed the following structural features: i) the length of "c" - 473 nucleotides; ii) the 3' terminal domain of src, ending in an amber codon at the 5'boundary of "c"; iii) terminator codons that preclude continuous translation from "c"; iv) suitably located sequences that may serve as signals for the initiation of viral RNA synthesis and for the processing and/or polyadenylation of viral mRNA; v) a repeated sequence that flanks src and that could facilitate deletion of this gene; vi) repeated sequences within "c"; and vii) unexplained homologies between sequences in "c" and sequences in several other nucleic acids, including the 5' terminal domain of the ASV genome, tRNATrp and its inversion, the complement of tRNATrp and its inversion, and the 18S RNA of eukaryotic ribosomes. We conclude that "c" probably does not encode a protein, but its sequence may nevertheless serve several essential functions in viral replication.

Alpharetrovirus↗
PubMed1979

tRNATrp as primer for RNA-directed DNA polymerase: structural determinants of function.

The specific interactions between the RNA-directed DNA polymerase of avian oncornavirus and the tRNATrp primer required for initiation of viral DNA synthesis in vitro were examined. Two distinct interactions, stable binding of the tRNATrp to the enzyme and initiation of viral DNA synthesis by the enzyme with tRNATrp as primer, were characterized as to the structure of tRNATrp required. Different structural features of the tRNATrp were shown to be necessary for each type of interaction. The entire primary structure and native conformation of tRNATrp are both required for binding to reverse transcriptase. Fragments of tRNATrp and intact tRNATrp in an altered conformation cannot be bound by the enzyme using an assay which detects high affinity binding between reverse transcriptase and native tRNATrp. In contrast, fragments of the tRNATrp molecule can serve as primers for viral DNA synthesis with normal efficiency as compared to intact tRNATrp. The fragments which initiate transcription must contain a minimum specific nucleotide sequence which extends from the 3' terminus of the tRNATrp through 27 residues of the molecule. This portion of the tRNATrp may be a major structural determinant of specificity in initiation.

Alpharetrovirus↗