Differential expression of two mRNAs from a single gene encoding an HMG1-like DNA binding protein of African trypanosomes.

We have isolated cDNA clones expressing a member of the high mobility group (HMG) protein family by screening a Trypanosoma brucei rhodesiense expression cDNA library with multimerized oligonucleotides corresponding to an octamer transcriptional regulatory sequence motif. The trypanosome DNA binding protein (TDP-1) encoded by these cDNAs contains two domains that show striking sequence similarity to the consensus sequence for HMG1-like DNA binding domains (HMG boxes). Southern blot analysis is consistent with TDP-1 being encoded by a single copy gene. The cDNA clones are derived from 2 mature mRNA species of approximately 1.6 and 2.3 kb in length that are generated by differential polyadenylation at sites 563 nucleotides and 1113 nucleotides downstream from the stop codon. Stage specific differences exist in the steady state levels of the 2 mRNAs: bloodstream parasites contain predominantly the 1.6-kb mRNA, while procyclic culture forms express predominantly the 2.3-kb mRNA.