Conserved sequences and transcription of the hsp70 gene family in Trypanosoma brucei.

Five Trypanosoma brucei 70-kilodalton heat shock protein-encoding genes (hsp70 genes) were found to be arranged in a tandem array. These hsp70 genes are separated by highly conserved intergenic region sequences of 200 base pairs for one gene and 234 base pairs for the other four genes. This intergenic region sequence is also present in front of the first gene of the tandem array, though at a further distance. All five conserved intergenic regions have sequences that are homologous to the eucaryotic control elements, essential for temperature-induced initiation of transcription by polymerase II. In addition, there is a T-rich region at the 3' end of the hsp70 genes which is homologous to the site of transcription termination of mini-exon genes. Immediately 3' of a putative TATA box, a branch point consensus sequence and six sequences homologous to known trypanosome 3' splice sites were found. It is therefore possible that a PolII promoter is present in the intergenic region sequence. Addition of the 35-nucleotide mini-exon to the hsp70 transcript could thus be mediated by bimolecular splicing. The importance of temperature control for development was illustrated by the response of variant surface glycoprotein-encoding genes to heat shock.