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 DN A target is highly sequence-specific. We provide data showing that PTB interacts with the top strand of the adenovirus major late promoter t ranscriptional initiator, a sequence rich in pyrimidine residues. We a lso demonstrate that PTB is organised into at least two different bind ing domains.