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Polyoma DNA: a physical map
Abstract:
The action of restriction enzymes on polyoma DNA was studied with uniformly (32)P-labeled viral DNA obtained from either infected 3T6 or secondary mouse-embryo cells. Three restriction enzymes were used to construct a physical map of the polyoma genome. An enzyme from Hemophilus parainfluenzae, Hpa(II), cleaved polyma DNA into eight unique fragments (Hpa(II)-1 to Hpa(II)-8), ranging in size from 27.3 to 1.8% of the genome. An enzyme from Hemophilus influenzae, Hin(III), gave two fragments (56 and 44%); and a third enzyme from Escherichia coli, EcoR(I), cut at a single unique site. The physical map of the polyma genome was constructed from methods involving: (1) further digestion of the fragments produced by enzymes EcoR(I) and Hin(III) with Hpa(II), and (2) analysis of the products of partial digestion with Hpa(II). Analysis by electron microscopy of replicating DNA molecules (less than 50% replicated) cut with the Hin(III) enzyme, in combination with other studies, has indicated that the origin of DNA replication is located at 71 +/- 3 map units from the EcoR(I) cleavage site, probably in Hpa(II)-5.
Insights
Researchers mapped the polyoma virus genome using restriction enzymes Hpa(II), Hin(III), and EcoR(I). They located the DNA replication origin at 71 map units from the EcoR(I) site, likely within the Hpa(II)-5 fragment.
Area of Science:
- Molecular Biology
- Virology
- Genomics
Background:
- Polyoma virus is a small DNA tumor virus extensively studied in molecular biology.
- Understanding the polyoma genome structure is crucial for studying viral replication and oncogenesis.
Purpose of the Study:
- To construct a detailed physical map of the polyoma virus genome.
- To identify the origin of viral DNA replication.
Main Methods:
- Utilized three restriction enzymes: Hpa(II) (Hemophilus parainfluenzae), Hin(III) (Hemophilus influenzae), and EcoR(I) (Escherichia coli).
- Employed Southern blotting and partial digestion analyses for fragment mapping.
- Used electron microscopy to analyze replicating DNA molecules and determine the replication origin.
Main Results:
- Hpa(II) digestion yielded eight unique fragments, Hin(III) produced two fragments, and EcoR(I) cleaved at a single site.
- A comprehensive physical map of the polyoma genome was established.
- The origin of DNA replication was mapped to 71 +/- 3 units from the EcoR(I) site, likely within the Hpa(II)-5 fragment.
Conclusions:
- The study successfully established a high-resolution physical map of the polyoma genome.
- The precise location of the DNA replication origin provides insights into viral replication mechanisms.