Figure 1.

Yeast mitochondrial protein extracts ligate nicked DNA:DNA substrates. Mitochondrial protein extracts were prepared from strain 2780-49BWT, cdc9-1^ts and Δdnl4 yeast and their ability to seal a nick in a DNA:DNA duplex substrate was assayed. Reactions were carried out as described in Materials and Methods, with extracts preincubated at the temperatures indicated. The lower band indicates unligated substrate DNA, while the upper band (arrow) indicates the ligated DNA product. The positive control (+) is substrate plus T4 DNA ligase; the negative control (–) is substrate alone.