PTF1 encodes an essential protein in Saccharomyces cerevisiae, which shows strong homology with a new putative family of PPIases.

Complementation of a temperature sensitive mutant of the yeast Saccharomyces cerevisiae resulted in the isolation of PTF1 (processing/termination factor 1), an essential gene encoding a putative 3'-end processing or transcription termination factor of pre-mRNAs. Ptf1p shows significant homology to a newly discovered family of PPIases. This family is characterized by its insensitivity to immunosuppressive drugs and the lack of homology with cyclophilins and FK-506 binding proteins [Rahfeld et al. (1994) FEBS Lett. 352, 180-184]. Should Ptf1p display PPIase activity, it would be the first characterized, eukaryotic member of this putative family, which is essential for growth.