Fig. 1. lacI-HP1 association silences heat shock inducible expression of hsp26 and hsp70 reporter genes. (A) The lac-hsp26-hsp70 reporter contains 256 lac operator sites positioned 1.9 and 3.7 kb upstream from the transcriptional start site of the heat shock inducible promoters hsp26 and hsp70, respectively. The hsp26 gene is fused to a barley cDNA fragment as a unique sequence tag and hsp70 is fused to the white reporter gene as a transformation marker. (B) RNA was isolated from adult flies carrying either the lac-hsp26-hsp70 reporter transposon alone, the GFP-lacI expressor and the reporter transposon, or the lacI-HP1 expressor and the reporter transposon. The flies were raised with daily heat shock treatments or non-heat shock conditions. RNA was analyzed for hsp26-tag expression (upper autoradiograph) and rp49 expression (lower autoradiograph) as a loading control. (C) Northern analysis of hsp70-white expression (upper autoradiograph) and rp49 expression (lower radiograph).