The large mutant R-factor R1drd-19B2 gives rise to several classes of small, covalently closed circular deoxyribonucleic acids (DNAs), designated as Rsc DNAs, when harbored by the K-12 strain CRT46 which carries a dnaA mutation. The molecular weights of these DNA molecules range from 3 X 106 to 8.4 X 106. Cells arising from single colonies of CRT46-R1drd-19B2 harbor only one to two copies of the large mutant R-factor and in addition 10 to 20 copies of Rsc plasmid of a discrete size class per chromosome. The larger Rsc DNAs carry the ampicillin resistance gene. After transformation the small circular DNAs are present in Escherichia coli C in a large number of copies, up to 100 copies per chromosome. Hybridization studies between Rsc plasmids indicate that they possess common DNA sequences.

No abstract

Starting from a cosmid library of HCMV Ad169-DNA random fragments of DNA were generated. Fragments about 200 to 600 bp in length were selected and cloned into open reading frame (ORF) expression vectors to create ORF-libraries that represent either the entire viral genome or defined subregions. About 120,000 clones were isolated and screened immunologically for the synthesis of fusion proteins consisting of an antigenic peptide encoded by the CMV sequence coupled to a truncated E. coli beta-galactosidase molecule. Anti-CMV sera raised in animals as well as human hyperimmune globulin were used for colony screening. Distinct sets of antigenic fusion proteins were recognized by different antisera. Ten of the clones giving strong reactions with human immune sera were mapped on the CMV genome and the sequences of the CMV inserts determined. Antibodies against fusion proteins were raised in mice or rabbits to identify the corresponding CMV proteins. Antigenic fusion proteins described here were recognized by most individual human CMV immune sera tested. They allow determination of the humoral immune response to defined determinants and may therefore be particularly useful in diagnosis and vaccine development.