摘要：

The DNA polymerase ("reverse transcriptase") has been isolated from virions of two temperature-sensitive Rous sarcoma virus mutants (ts335 and ts337). These mutants are defective at an early stage of both growth and transformation. The purified polymerase is three-fold more rapidly inactivated by heat than is wild type polymerase. The ribonuclease H activity of the mutant enzyme also shows an increased heat-lability when compared to the wild type activity. Studies on recombinants of the mutants with an avian leukosis virus indicate that the defects in growth and transformation are caused by the heat-lability of the DNA polymerase. These studies strongly support the idea that the virion DNA polymerase of RNA tumor virus is needed to synthesize a DNA copy of the viral genome soon after the infection of a cell by an RNA tumor virus.

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