The Leptomonas seymouri spliced leader RNA promoter requires a novel transcription factor

The spliced leader RNA gene promoter in Leptomonas seymouri requires three promoter elements for efficient and accurate transcription of the spliced leader RNA. The upstream most element appears to have a functional homolog in Leishmania species and in the African trypanosomes. The protein factor, promoter binding protein-1, interacts with the upstream element and appears to function as a basal transcription factor. Promoter binding protein-1 has three subunits; 36, 41 and 57 kDa. Using microsequencing techniques, we have obtained peptide sequence from each subunit. These data have enabled us to recently identify the Leptomonas gene that encodes the 41 kDa subunit. The 41 kDa subunit, comprised of 381 amino acids, is a founding member of a new class of transcription factors since extensive database searches revealed no homology to any known protein. This subunit, encoded by a single copy gene, has a potential nuclear localisation signal at amino acid positions 71-76. There are also multiple dileucine repeats with unknown function. Anti-41 kDa protein polyclonal antibodies are being employed to test the function of the 41 kDa subunit in PBP-1 activities.