R. Levyholtzman et al., DIFFERENCES IN DNA-SEQUENCE RECOGNITION BY THE HEAT-SHOCK FACTORS OF DROSOPHILA-MELANOGASTER AND THE PARASITIC HELMINTH SCHISTOSOMA-MANSONI, Biochimica et biophysica acta, N. Gene structure and expression, 1264(1), 1995, pp. 134-140
It was recently shown that schistosome extracts contain heat-shock fac
tor (HSF) activity that correlates with the pattern of hsp70 mRNA leve
ls at different developmental stages of the parasite (Levy-Holtzman an
d Schechter (1993) Parasitology 108, 35-42). To extend our understandi
ng of the HSF activity revealed in extracts of Schistosoma mansoni (Sm
), it was further analyzed by competition experiments and compared wit
h the well characterized HSF of Drosophila melanogaster (Dm. The inter
actions of HSF in Sm extracts (SmHSF) and HSF of Dm (DmHSF) with P-32-
labeled heat shock element (HSE) probes, with and without unlabeled co
mpetitor DNA probes (HSE-related oligos), were analyzed by gel retarda
tion assay. The binding and inhibition studies demonstrated that SmHSF
and DmHSF differ in HSE sequence recognition: an array of three nGAAn
inverted repeats according to the ideal consensus sequence (nGAAnnTTC
nnGAAn) is recognized by DmHSF, but not by SmHSF. In the schistosome,
binding is attained only when the third pentamer is a variant, compose
d of nGTAn instead of nGAAn. The presence of this variant in the promo
ter of the hsp70 gene of the parasite suggests coevolution of the vari
ant sequence together with the SmHSF which interacts efficiently with
the variant, but not with the ideal HSE sequence. Further inhibition s
tudies revealed additional differences between SmHSF and DmHSF in reco
gnition of the first and second nGAAn pentamers of HSE. In analogy to
other systems of ligand-protein interactions, we propose that the comp
lementarity between the HSE ligand and the HSF protein is higher in Sm
HSF, as compared to DmHSF.