Lois Ann Salzman

Formation of intermediates in the replication of phage lambda DNA

After induction of Escherichia coli K12(λ) by ultraviolet light, a large part of the newly synthesized DNA is present as intermediate forms which are clearly distinguishable from mature λ DNA. One of the new DNA species is very sensitive to shearing and shows a relatively high sedimentation rate when compared to normal λ DNA. Its properties are consistent with those of a long, linear, concatenated structure. The intermediate forms of λ DNA are apparently formed from smaller DNA molecules the size of mature λ DNA. In the latter part of the latent period just before cell lysis, these large intermediates are broken down to DNA of the size found in the normal phage particle. λsusA and λsusD mutants have been found to accumulate large amounts of the intermediate during λ DNA synthesis and are unable to convert them to mature phage DNA.

Structural proteins of kilham rat virus

Abstract The protein composition of KRV was determined by dissociation of radioactive virion particles. The protein subunits were separated by electrophoresis on polyacrylamide gels and by agarose gel filtration in 6 M guanidine-HCl. Three major viral proteins were found of molecular weights approximately 72,000, 62,000 and 55,000 daltons. The protein component with a molecular weight of 62,000 daltons comprised about 75.5% of the total virion protein and is believed to be capsid protein.

Studies on the formation of circular λ DNA

Abstract A circular form of λ DNA is synthesized within 5 minutes after phage infection of sensitive and lysogenic cells of Escherichia coli K12 at phage multiplicities of 5 and 0.8 phage per bacterium. The amount of circular λ DNA formed in infected lysogenic cells is 2 to 3 times that found in sensitive cells infected under comparable conditions. The circular DNA species is also synthesized when λ phage superinfects lysogenic cells which had previously been induced by ultraviolet light or thymine deprivation. Although the mechanism for synthesis of the circular λ DNA species is not known, evidence is presented that it does not involve the incorporation of thymine or inorganic phosphate.

Evidence for terminal S1-nuclease-resistant regions on single-stranded linear DNA.

Abstract The 5′- and probably the 3′-termini of the single-stranded linear DNA from parvovirus Kilham rat virus (KRV) are resistant to a single-stranded specific S, nuclease and elute from BND cellulose as a double-stranded DNA. These DNA pieces are small, involving 90 to 150 nucleotides from each end of the DNA molecule. The double-stranded DNA termini could result from hairpin turns of terminal palindromic sequences. The 3′ double-stranded DNA termini might serve as a primer for the replication of linear, single-stranded DNA.

Replication of Parvovirus DNA

In 1959, Kilham and Oliver characterized a virus that they isolated from several strains of metastasizing rat liver sarcomas and a transplantable leukemia. The virus named Kilham rat virus (KRV) caused a cytopathic effect (CPE) in rat embryo tissue, agglutinated guinea pig red blood cells (HA), was heat stable and ether resistant (1). Acridine orange and Feulgen stains of intranuclear inclusions in infected cells established that the virus contained DNA (2). KRV was the first characterized member of what is now a large group of viruses called parvoviruses. Parvoviruses are among the smallest eukaryotic viruses. They are ubiquitous and have been isolated from a wide variety of hosts. The parvoviruses that have been studied most include the H-l virus from a human transplantable tumor (3), bovine hemad- sorbing enteric virus (Haden; 4), bovine parvovirus (BPV; 5), feline pan- leukopenia virus (FPV; 6), minute virus of mice (MVM; 7), KRV (1), and human adeno-associated viruses (AAV; 8, 9).

Isolation of nucleoprotein from the parvovirus KRV

Abstract Disruption of the parvovirus KRV in alkali followed by sedimentation in sucrose at pH 10.0 results in the separation of the virion single-stranded DNA into two discrete sedimentation peaks. The first peak-at 16 S has the sedimentation value reported for purified KRV single-stranded linear DNA. The DNA has a mean contour length of 1.53 ± 0.19 μm which agrees closely with the previously reported length of KRV-DNA. The second DNA peak at 8–10 S contains DNA of approximately unit length and two subunit fragments. The fragments could result from the breakage of KRV-DNA at one specific point. The 8–10 S peak material appears to also contain protein and DNA polymerase activity. The protein may be complexed with the viral DNA since the density of the DNA in cesium chloride (1.66–1.69 g/ml) is altered from that found with purified KRV-DNA (1.72–1.73 g/ml). The importance of the nucleoprotein peak and its possible role in viral replication are discussed.