Biomaterial Database

Simian virus 40 DNA replication: characterization of gaps in the termination region. 1976

M C Chen, and E Birkenmeier, and N P Salzman

A class of precursor DNA (pDNA) II molecules has been identified as the immediate precursor of simian virus 40 DNA I. A pDNA II molecule contains a strand of newly synthesized DNA with an interruption located in the region where DNA synthesis terminates (4). These pDNA II molecules have been isolated and further characterized. They are converted to covalently closed structures (simian virus 40 DNA I) only when they are treated in vitro with both T4 DNA polymerase and Escherichia coli ligase. After in vitro repair of pDNA II with T4 DNA polymerase and nucleoside triphosphates, approximately 7 mol of alpha-[32P]dATP is incorporated per mol of DNA II. Alkaline sucrose analysis of these gap-filled molecules, after they have been cleaved with Eco RI restriction endonuclease, has demonstrated that gaps are specifically located in the termination region. alpha-[32P]dATP is incorporated equally into the two labeled products that are generated by RI cleavage of these molecules. This indicates the presence of gaps in both the newly synthesized plus the minus strands. Electrophoretic analysis of the gap-filled molecules, after they have been cleaved with endonuclease Hind, has shown that gaps are localized in Hind fragments G and B and to a minor degree in fragment J. pDNA II molecules have the following properties. There is a gap in the newly synthesized linear DNA strand contained in the pDNA II molecule. Nicked pDNA II molecules cannot be detected. The two molecules that arise by segregation contain gaps in both of the complementary strands. Based on the amount of alpha-[32P]dATP incorporated and the rate of exonuclease III digestion of gap-filled molecules, it is estimated that the size of the gaps is between 22 and 73 nucleotides. Models for termination of DNA synthesis are proposed based on these findings.

UI	MeSH Term	Description	Entries
D008025	Ligases	A class of enzymes that catalyze the formation of a bond between two substrate molecules, coupled with the hydrolysis of a pyrophosphate bond in ATP or a similar energy donor. (Dorland, 28th ed) EC 6.	Ligase,Synthetases,Synthetase
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D009694	Nucleic Acid Precursors	Use for nucleic acid precursors in general or for which there is no specific heading.	Acid Precursors, Nucleic,Precursors, Nucleic Acid
D002474	Cell-Free System	A fractionated cell extract that maintains a biological function. A subcellular fraction isolated by ultracentrifugation or other separation techniques must first be isolated so that a process can be studied free from all of the complex side reactions that occur in a cell. The cell-free system is therefore widely used in cell biology. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p166)	Cellfree System,Cell Free System,Cell-Free Systems,Cellfree Systems,System, Cell-Free,System, Cellfree,Systems, Cell-Free,Systems, Cellfree
D004260	DNA Repair	The removal of DNA LESIONS and/or restoration of intact DNA strands without BASE PAIR MISMATCHES, intrastrand or interstrand crosslinks, or discontinuities in the DNA sugar-phosphate backbones.	DNA Damage Response
D004261	DNA Replication	The process by which a DNA molecule is duplicated.	Autonomous Replication,Replication, Autonomous,Autonomous Replications,DNA Replications,Replication, DNA,Replications, Autonomous,Replications, DNA
D004262	DNA Restriction Enzymes	Enzymes that are part of the restriction-modification systems. They catalyze the endonucleolytic cleavage of DNA sequences which lack the species-specific methylation pattern in the host cell's DNA. Cleavage yields random or specific double-stranded fragments with terminal 5'-phosphates. The function of restriction enzymes is to destroy any foreign DNA that invades the host cell. Most have been studied in bacterial systems, but a few have been found in eukaryotic organisms. They are also used as tools for the systematic dissection and mapping of chromosomes, in the determination of base sequences of DNAs, and have made it possible to splice and recombine genes from one organism into the genome of another. EC 3.21.1.	Restriction Endonucleases,DNA Restriction Enzyme,Restriction Endonuclease,Endonuclease, Restriction,Endonucleases, Restriction,Enzymes, DNA Restriction,Restriction Enzyme, DNA,Restriction Enzymes, DNA
D004279	DNA, Viral	Deoxyribonucleic acid that makes up the genetic material of viruses.	Viral DNA
D004926	Escherichia coli	A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.	Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D013539	Simian virus 40	A species of POLYOMAVIRUS originally isolated from Rhesus monkey kidney tissue. It produces malignancy in human and newborn hamster kidney cell cultures.	SV40 Virus,Vacuolating Agent,Polyomavirus macacae,SV 40 Virus,SV 40 Viruses,SV40 Viruses,Vacuolating Agents