No abstract

Intracisternal A particles from the FLOPC-1 line of BALB/c myeloma have been shown to contain high-molecular-weight RNA (60 to 70S) that is sensitive to RNase, alkali degradation, and heat but resistant to Pronase treatment. The intracisternal A-particle RNA contains tract of poly (A) approximately 180 nucleotides long. As shown in a reconstitution experiment, by antigenic analysis of A-particle preparation and the SC cytopathogenicity assay, the 70S RNA was not due to contamination by type C virus particles. The FLOPC-1 intracisternal A particles also possess an endogenous RNA-dependent DNA polymerase. The enzyme required Mn2+ or Mg2+, dithiothreitol, detergent, and four deoxyribonucleoside triphosphates for maximum activity. Enzymatic activity was maximally stimuated by poly (rC)-oligo (dG)12-18 and less with poly (rG)-oligo (dC)10 or poly (rA)-oligo (dT)12-18 as compare with synthetic DNA/DNA duplex templates such as poly (dA)-oligo (dT)12-18. The enzyme can utilize the A-particle endogenous RNA as template as shown by analysis of the early and late DNA products of the endogenous reaction by CsSO4 isopycnic gradient centrifuation and hybridization of purified 70S or 35S A-particle RNA with the purified complementary DNA product. Approximately 50% of the A-particle complementary DNA also hybridized with oncornavirus RNA.

C-type particles produced by a tissue culture-adapted BALB/c myeloma were characterized. It was determined that although the particles were morphologically and antigenically similar to murine leukemia and sarcoma virus, the size of their RNA was different, they lacked RNA-dependent DNA polymerase, they were unstable in NET buffer, sucrose and citrate but were stable in glycerol and Earle balanced salt solution, and they behaved differently from oncornaviruses when treated with ether and detergent. Murine myelomas in culture have been reported to produce an RNA-containing virus with antigenicity, morphology, nucleic acid type (RNA), size (74S), and base composition similar to murine leukemia virus (MuLV) (43). The myeloma viruses Watson et al. (43) studied were all from oil-induced tumors except for those from the C-1 cell line, a spontaneous myeloma of a C3H mouse. Aoki et al. (3) showed that the C-type particle produced by MOPC-70A possessed the G (Gross) viral envelope antigen (GVEA) and XVEA, a viral enve

No abstract

Streptomycin inhibits protein synthesis in bacteria by interfering with ribosomal function. SM\1 inhibited the incorporation of amino acids in undefined cell-free systems from Escherichia colil 2 and decreased polyphenylalanine synthesis in E. coli ribosomes when poly U was used as messenger." It was suggested that SMAI acts by interfering with either the attachment or functioning of poly U on the ribosome. SMl did not prevent attachment of poly U to ribosomes, but the presence of poly U on ribosomes made the SM binding site less accessible to the antibiotic. This binding site is on the 30S ribosomal subunit, the one to which messenger also binds.7 Davies et al.8 showed that in E. coli ribosomes with poly U as messenger, SM decreased incorporation of phenylalanine and increased incorporation of isoleucine. Thus, SM altered the translation process whereby the information of the messenger was decoded. Davies et al.8 suggested that S\I acts on intact bacteria, not by inhibiting protein synthesis, but by causing the synthesis of nonfunctional proteins with altered amino acid sequences. Pestka et al.9 have recently