mRNA analysis for mre11, rad50, and mre11-rad50 genes in the background strain, deletion mutants, and wild-type Halobacterium. (A and B) RT-PCR analysis showing the presence or absence of mRNA transcripts in the AK071 background strain (lane 1), AK073 (Δrad50) (lane 2), AK072 (Δmre11) (lane 3), and wild-type Halobacterium (lane 4). A 500-bp fragment of the transcript from mre11 was identified in AK071, AK073, and the wild type but was lacking in AK072, as expected (A). A 500-bp fragment of the transcript from rad50 was identified in AK071, AK072, and the wild type but was lacking in AK073, as expected (B). (C) Northern hybridization blot showing the absence of mRNA transcription in AK073 (Δrad50) compared to the observed mRNA in AK071 (background strain). DNA probes were designed to hybridize to a 500-bp region within the rad50 transcript.