The polypyrimidine tract binding (PTB) protein interacts with single-stranded DNA in a sequence-specific manner

Polypyrimidine tract binding (PTB) protein is a cellular factor whose function is unknown. Various RNA or single-stranded DNA sequences have been shown to interact with PTB. In this paper, using laser UV cross-linking and electrophoretic mobility shift assays to probe DNA-protein interactions, we demonstrate that PTB binding at a single-stranded DNA target is highly sequence-specific. We provide data showing that PTB interacts with the top strand of the adenovirus major late promoter transcriptional initiator, a sequence rich in pyrimidine residues. We also demonstrate that PTB is organised into at least two different binding domains.