Life span (turnover) of zrfA and zrfB mRNA after repression of transcription by zinc. Strain AF14 was grown in complete SD medium without a supplement of zinc for 20 h, and a sample was taken (lane 1, −Zn). At this point, the culture was supplemented with 100 μM zinc and samples were collected and immediately frozen in liquid nitrogen after 5, 10, 20, and 30 min. Probes are indicated to the left of each blot.