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K Beemon

Publications and source records attributed to K Beemon.

25 records · Page 2Linked to original sources
PubMed1977

In vitro translation yields a possible Rous sarcoma virus src gene product.

In vitro translation of Rous sarcoma virus (RSV) virion RNA in the messenger-dependent reticulocyte lysate system yielded polypeptides that were not synthesized by translation of RNA from a transformation-defective deletion mutant of RSV. These RSV-specific products migrated on sodium dodecyl sulfate/polyacrylamide gels as two doublets of approximately 25,000 and 17,000 daltons. Synthesis of these proteins was not sensitive to inhibition by m7GTP; however, synthesis of the 76,000-dalton precursor of the internal structural proteins was sensitive to inhibition by m7GTP. Tryptic peptide maps showed the 25,000- and 17,000-dalton proteins to be related to one another but to be distinct from the 76,000-dalton protein. The 25,000-dalton protein was translated only from a polyadenylylated RNA of approximately 2500 nucleotides, whereas the 76,000-dalton protein was translated from 38S RNA, corresponding to the entire viral genome. A 180,000-dalton protein was also synthesized from 38S RSV virion RNA. From the absence of the 25,000- and 17,000-dalton proteins in the translation products of transformation-defective RSV RNA and the size of their RNA templates, we conclude that these proteins may be derived from coding sequences within the RSV src gene.

Animals↗
PubMed1977

Relationship between Moloney murine leukemia and sarcoma virus RNAs: purification and hybridization map of complementary DNAs from defined regions of Moloney murine sarcoma virus 124.

Complementary DNAs (cDNA's) specific for various regions of the Moloney murine sarcoma virus (MSV) 124 RNA genome were prepared by cross-hybridization techniques. A cDNA specific for the first 1,000 nucleotides adjacent to the RNA 3' end (cDNA 3') was prepared and shown to also be complementary to the 3'-terminal 1,000 nucleotides of a related Moloney murine leukemia virus (MLV) genome. A cDNA complementary to the "MSV-specific" portion of the MSV 124 genome was prepared. This cDNA was shown not to anneal to Moloney MLV RNA and to anneal to a portion of the viral RNA of about 1,500 to 1,800 nucleotides in length, located 1,000 nucleotides from the 3' end of MSV RNA. A cDNA common to the genome of MSV and MLV was also obtained and shown to anneal to the 5'-terminal two-thirds, as well as to the 3'-terminal 1,000 nucleotides, of the MSV RNA genome. This cDNA also annealed to the RNA from MLV and mainly to the 5'-terminal half of the MLV genome. It is concluded that the 6-kilobase Moloney MSV 124 RNA genome has a sequence arrangement that includes (i) a 3' portion of about 1,000 nucleotides, which is also present at the 3' terminus of MLV; (ii) an MSV-specific region, not shared with MLV, which extends between 1,000 and 2,500 nucleotides from the 3' terminus; and (iii) a second "common" region, again shared with MLV, which extends from 2,500 nucleotides to the 5' terminus. This second common region appears to be located in the 5' half of the 10-kilobase MLV genome as well. Experiments in which a large excess of cold MLV cDNA was annealed to (3)H-labeled polyadenylic acid-containing fragments of MSV RNA gave results consistent with this arrangement of the MSV genome.

Base Sequence↗
PubMed1976

Sequences and functions of Rous sarcoma virus RNA.

A procedure has been developed to map the genetic elements of avian tumor virus RNA, which has a molecular weight of about 3 X 10(6) daltons and a poly(A) sequence at the 3' end. For this purpose, about 30 RNase T1-resistant oligonucleotides were ordered relative to the 3'-poly(A) terminus of the RNA, to construct an oligonucleotide map of viral RNAs. A cluster of seven envelope gene (env)-specific oligonucleotides, identified by their absence from the otherwise very similar oligonucleotide map of an envelope-defective deletion mutant (which lacks the major viral glycoprotein), mapped at a distance of 0.9 to 1.6 X 10(6) daltons from the poly(A) end of sarcoma virus RNA. A cluster of three sarcoma gene (src)-specific oligonucleotides, identified by their absence from the otherwise nearly identical oligonucleotide map of a transformation-defective deletion mutant mapped at a distance of 0.2 to 0.6 X 10(6) daltons from the poly(A) end of sarcoma virus RNA. The oligonucleotide maps of sarcoma viruses and of related deletion mutants were the same from the poly(A) end up to 0.2 X 10(6) daltons and included one terminal oligonucleotide, termed C, which is found in all avian tumor viruses tested so far. Preliminary mapping experiments ordering the src-specific and env-specific oligonucleotides of recombinants, selected for sarcoma and envelope genes of different parents, agree with those obtained by comparing maps of wild type viruses and deletion mutants. A partial genetic map consistent with these results suggests that the src gene maps between the env gene and the 3'-poly(A) end of viral RNA. This map reads: poly(A)-src-env-(pol, gag).

Avian Sarcoma Viruses↗
PubMed1976

The 30S Moloney sarcoma virus RNA contains leukemia virus nucleotide sequences.

The 50S-70S RNA of a Moloney sarcoma-leukemia virus [Mo-MSV(MLV)] complex produced by a particular mouse cell line was shown by gel electrophoresis to contain a major (97%) 30S sarcoma-specific subunit species and a minor (3%) 38S leukemia virus-specific subunit. On the basis of its sedimentation coefficient and known complexity, the 30S Mo-MSV RNA was estimated to be a unique RNA molecule of about 6000 nucleotides. Hybridization experiments using viral RNA and DNA complementary to viral RNA (cDNA) made by viral DNA polymerase indicated that the 30S Mo-MSV RNA shared 70% of its sequences with Mo-MLV, 30% with another MLV derived from Mo-MLV, and 30% with Kirsten sarcoma-xenotropic leukemia virus. The 30S Mo-MSV RNA sequences shared with these viruses were not additive. The Tm of a Mo-MSV RNA-MLV cDNA hybrid was 83 degrees C, indicating that large contiguous nucleotide sequences were shared between the two nucleic acids. Mo-MSV RNA and Mo-MLV RNA shared possibly seven of 20-30 RNAase T1-resistant oligonucleotides, while Mo-MSV RNA contained three, and Mo-MLV RNA contained at least five specific oligonucleotides. We conclude that the 30S Mo-MSV RNA molecule consists of approximately 70% (about 4200 nucleotides) Mo-MLV-specific sequences and of 30% (1800 nucleotides) Mo-MSV-specific sequences covalently linked. Our results favor the hypothesis that 30S Mo-MSV RNA was generated by recombination between Mo-MLV and other genetic elements. We discuss whether all or only the MSV-specific sequences of the 30S Mo-MSV RNA function as sarcoma genes. Mo-MLV cDNA was hybridized about 45% by unfractionated Mo-MSV (MLV) RNA at RNA/DNA ratios of up to 10, about 50% by electrophoretically purified 30S Mo-MSV RNA at RNA/DNA ratios up to 500, but close to 100% by unfractionated Mo-MSV(MLV) RNA at RNA/DNA ratios over 900. This indicated that unfractionated RNA of our Mo-MSV(MLV) contained a complete complement of Mo-MLV, albeit at a low ratio.

Base Sequence↗
PubMed1975

Mapping RNase T1-resistant oligonucleotides of avian tumor virus RNAs: sarcoma-specific oligonucleotides are near the poly(A) end and oligonucleotides common to sarcoma and transformation-defective viruses are at the poly(A) end.

The large RNase T1-resistant oligonucleotides of the nondefective (nd) Rous sarcoma virus (RSV): Prague RSV of subgroup B (PR-B), PR-C and B77 of subgroup C; of their transformation-defective (td0 deletion mutants: td PR-B, td PR-C, and td B77; and of replication-defective (rd) RSV(-) were completely or partially mapped on the 30 to 40S viral RNAs. The location of a given oligonucleotide relative to the poly(A) terminus of the viral RNAs was directly deduced from the smallest size of the poly(A)-tagged RNA fragment from which it could be isolated. Identification of distinct oligonucleotides was based on their location in the electrophoretic/chromatographic fingerprint pattern and on analysis of their RNase A-resistant fragments. The following results were obtained. (i) The number of large oligonucleotides per poly(A)-tagged ffagment increased with increasing size of the fragment. This implies that the genetic map is linear and that a given RNase T1-resistant oligonucleotides has, relative to the poly(A) end, the same location on all 30 to 40S RNA subunits of a given 60 to 70S viral RNA complex, (ii) Three sarcoma-specific oligonucleotides were identified in the RNAs of Pr-B, PR-C and B77 by comparison with the RNAs of the corresponding td viruses...

Avian Sarcoma Viruses↗
PubMed1974

Evidence for crossing-over between avian tumor viruses based on analysis of viral RNAs.

The RNAs of several avian tumor virus recombinants that had inherited their focus-forming ability from a sarcoma virus and their host range marker from a leukosis virus were investigated. Electrophoretic analyses showed that the cloned sarcoma virus recombinants contained only size class a RNA, although they had acquired a marker that resided on class b RNA in the leukosis virus parent. Class a RNA of different recombinant clones, derived from the same pair of parental viruses and selected for the same biological markers, differed slightly in electrophoretic mobility from each other and from the parental sarcoma virus. They were also found to have different fingerprints of RNase T1-resistant oligonucleotides. The average complexity of the 60-70S RNA prepared from Prague Rous sarcoma virus of subgroup B was estimated to be 3.5 x 10(6) daltons from the size of 20 RNase T1-resistant oligonucleotides, which represented 3.9% of the RNA and that of a recombinant to be 3.3 x 10(6) daltons from 23 oligonucleotides, which represented 4.7% of the RNA. This result suggests that the genome of wild-type and of recombinant RNA tumor viruses is polyploid. The sum of these observations led us to propose that recombination among avian tumor viruses occurred by crossing-over between homologous pieces of nucleic acid.

Alpharetrovirus↗