Selective DNA Repair in the Transcribed Strands of Active Genes in Mammalian Cells

Abstract

Cyclobutane pyrimidine dimers are preferentially removed from transcriptionally active genes: (i) In Chinese hamster cells which remove only a small fraction of dimers from their total DNA, dimers are efficiently removed from the transcriptionally active dihydrofolate reductase (DHFR) gene and poorly removed from a sequence near the gene (Bohr et al., 1985). (ii) In mouse cells which also remove only a small fraction of dimers from their total DNA, dimers are proficiently removed from the transcriptionally active c-abl gene and poorly removed from the inactive c-mos gene (Madhani et al., 1986). (iii) In repair proficient human cells, dimers are removed more rapidly from the active DHFR gene than from bulk DNA or from the nontranscribed repetitive alpha sequences (Mellon et al., 1986). This work was recently reviewed by Smith (1987).