THE PARP AND RIBOSOMAL-RNA PROMOTERS OF TRYPANOSOMA-BRUCEI ARE COMPOSED OF DISSIMILAR SEQUENCE ELEMENTS THAT ARE FUNCTIONALLY INTERCHANGEABLE

The African trypanosomes express two major surface proteins, the varia nt surface glycoprotein (VSG) and the procyclic acidic repetitive prot ein (PARP). The RNA polymerase that transcribes the VSG and PARP genes shares many characteristics with RNA polymerase I. We show that altho ugh there is very little similarity in nucleotide sequence, the functi onal structure of a trypanosome rRNA promoter is almost identical to t hat of the PARP promoter. Further, domains from the PARP promoter can functionally substitute for the corresponding parts of the rRNA promot er, and vice versa.