INVITRO INTERACTION OF NUCLEAR PROTEINS WITH THE PROMOTER OF SOYBEAN HEAT-SHOCK GENE GMHSP17.5E

Proteins present in crude nuclear extracts of soybean (Glycine max) plumules were shown to bind in vitro to the 5′ flanking sequences of the soybean heat shock gene Gmhsp17.5E. The specificity of binding activity present in extracts from both control (28°C) and heat shocked (40°C) tissues was demonstrated by reciprocal competition experiments using gel mobility retardation assays. Footprinting experiments using DNase I with crude nuclear extracts indicated that a continuous stretch of 5′ flanking sequences extending from -40 to -153 was protected from digestion in vitro. Nuclear proteins that were partially purified by heparin agarose chromatography were shown to bind specific TATA-proximal sequences containing the heat shock consensus elements (HSEs) (-73 to -49; -107 to -84) and AT-rich motifs (-119 to -153). Other binding sites within AT-rich sequences (-906 to -888, -868 to 863, -859 to 853, and -841 to -830), distal HSE elements (-568 to -532) and a TATA/dyad (-234 to -207) were also identified by DNase I footprinting of TATA-distal probes. DNA binding activities specific for the HSE and AT-rich sequences were present in nuclear extracts from both control and heat shocked tissues. Both types of binding activity were increased after heat shock treatment; HSE binding increased from 1.8- to 2.7-fold, and binding to AT-rich sequences showed an increase from 1.3- to 1.7-fold.