FIG. 7.

DNA deletion is caused by hairpin RNAs. (A) PCR analysis of DNA from pools of ATU1hp cells mated with WT strain CU428. Mating cells were untreated (−), treated with Cd during starvation prior to mating (s), or treated with Cd at the indicated hour after initiating mating. DNA was prepared from cells 24 h after mixing. In the ATU1 locus diagram, the expressed gene is represented by an open arrow, with the region corresponding to the hairpin indicated by the joined horizontal lines; annealing locations of PCR primers are indicated by arrows under the gene diagram. Approximate borders of DNA deletion are represented by vertical parallel lines. Next to the PCR assay gel, arrows indicate PCR products consistent with DNA deletion, which are present in all Cd-treated samples. (B) Sequence analysis of deletion products. Two representative deletion boundaries are diagrammed, with the top line showing the WT sequence with deleted bases in italics, microhomologies in bold, and AT sequences underlined. The bottom line shows the sequence after deletion has occurred.