Polymorphism and stability of histone gene clusters in Drosophila melanogaster cultured cells

In a previous communication (Saigo, K., Millstein, L. and Thomas, C.A., Jr. (1981) Cold Spring Harbor Symp. Quant. Biol. 45, 815-827), the overall structure of histone genes of Schneider line 2 cells was shown to extensively differ from that of Oregon-R embryo from which the cell line was established, and it was speculated that the histone genes might be reshuffled extensively during either the periods of the establishment, or maintenance of cell lines, or both. To establish the validity of this notion the structure of histone genes was examined in Drosophila melanogaster cultured cells. The overall organization of histone gene clusters was found to be stably maintained in both the periods for the establishment and maintenance of cultured cells, indicating that the previous assumption is inadequate. Instead of an extensive rearrangement, minor structural changes were found to occasionally occur probably by simple base substitutions and/or, deletion or insertion of very short DNA pieces. It was also shown that the extensive variation in structures of histone genes in cultured cells such as Schneider line 2 are attributable to polymorphism on the level of individual flies.     

Synthesis of 2'-deoxy-6,3'-methano-cyclo-pyrimidine nucleosides

The nucleophilic attack of lithiated pyrimidines to a suitably-protected 3-ketosugar, afforded the 3-branched sugar stereospecifically, followed by intramolecular glycosylation to give 6,3'-methano-cyclo-pyrimidine nucleosides. The 2'-deoxygenation was achieved by sequential protection, deprotection and radical reduction.     

Molecular basis for the spontaneous generation of colonization-defective mutants of Streptococcus mutans

Spontaneous mutants of Streptococcus mutans GS-5 defective in sucrose-dependent colonization of smooth surfaces are generated at frequencies above the spontaneous mutation rate. Southern blot analysis of such mutants suggested rearrangement of the genes coding for glucosyltransferase (GTF) activity. Two strain GS-5 homologous tandem genes, gtfB and gtfC, coding for GTF-I and GTF-S activities respectively, were demonstrated to undergo recombination when introduced into recombination-proficient Escherichia coli transformants. However, the two genes were quite stable when transformed on a single DNA fragment into a recA mutant of E. coli. The DNA fragment coding for GTF activity from one S. mutans colonization-defective mutant, SP2, was isolated and shown also to have undergone recombination between the gtfB and gtfC genes, resulting in reduced GTF activity. These results are discussed relative to the in vivo generation of colonization-defective mutants in cultures of S. mutans.     

Antigenic variation among Sendai virus strains detected by monoclonal antibodies

Thirteen strains of Sendai virus isolated from various sources in the 1950's and after 1976 were compared for their reactivities with monoclonal antibodies prepared against the prototype strain MN of Sendai virus. Results revealed that while the 5 strains isolated in the 1950's reacted with all the monoclonal antibodies as the prototype strain did, the 2 strains isolated in 1976 and 1978 did not react with an F-specific monoclonal antibody, and the other 6 strains isolated after 1978 lacked reactivity with an HN-specific monoclonal antibody.