Figure 8
From: An internal ribosome entry site element directs the synthesis of the 80 kDa isoforms of protein 4.1R
PTB binds to the 4.1R sequence containing the IRES. 4.1R radiolabeled transcripts containing (583 nt) or lacking (149 nt) IRES activity (see Figure 7) were used in UV-crosslinking assays with reticulocyte lysate (RRL) proteins (A) or purified recombinant polypyrimidine tract-binding protein (PBT) (B). Following RNase A treatment, proteins were fractionated by 10% SDS-PAGE and autoradiographed. As a control, bovine serum albumin was added at the same molar concentration as PTB. A 150-molar excess of competitor to labeled probe was added where indicated.