Characterization of a Trypanosoma cruzi polypyrimidine tract binding protein interacting with single-stranded forming DNA

•  Although crucial to their biology, regulation of gene expression in trypanosomatid parasites is not fully understood. Our knowledge is limited to the fact that transcript levels are mainly determined post-transcriptionally. However, where and how transcription is initiated is largely unknown and few DNA and RNA binding proteins have been characterized. Therefore, identification of regulatory sequences and counteracting proteins will considerably improve our understanding of the parasite biology. In this work, we have characterized a novel protein in the protozoan parasite Trypanosoma cruzi named T. cruzi polypyrimidine tract binding protein (TcPTB) and investigated its potential role in transcription initiation. TcPTB shares structural and functional properties with mammalian PTB, a protein with multiple roles in mRNA metabolism and transcription initiation. We show that TcPTB is expressed in all parasite stages and is predominantly located in the nucleus. It binds in vitro to polypyrimidine-rich ssDNA including cis-regulatory elements implicated in transcription initiation in mammals and in the related parasite Leishmania major. Chromatin immunoprecipitation analysis associates TcPTB to the RNA pol II promoter of the spliced leader gene. Finally, we also show that T. cruzi polypyrimidine/polypurine sequences form triple helix, a condition necessary for the binding of mammalian PTB. These results suggest that TcPTB has a similar multifunctional role in gene regulation as in mammals.

Nyckelord

Trypanosoma cruzi

polypyrimidine-binding protein

CL Brener

TcPTB

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)