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  • Title: Inhibitory DNA ligands to platelet-derived growth factor B-chain.
    Author: Green LS, Jellinek D, Jenison R, Ostman A, Heldin CH, Janjic N.
    Journal: Biochemistry; 1996 Nov 12; 35(45):14413-24. PubMed ID: 8916928.
    Abstract:
    We have identified a group of DNA molecules that bind to platelet-derived growth factor (PDGF)-AB with subnanomolar affinity from a randomized DNA library using in vitro selection. Individual ligands cloned from the affinity-enriched pool bind to PDGF-AB and PDGF-BB with comparably high affinity (Kd approximately 10(-10) M) and to PDGF-AA with lower affinity (> 10(-8) M), indicating specific recognition of the PDGF B-chain in the context of the hetero- or homodimer. The consensus secondary structure motif for most of the high-affinity ligands is a three-way helix junction with a three-nucleotide loop at the branch point. Photo-cross-linking experiments with 5-iodo-2'-deoxyuridine-substituted ligands establish a point contact between a thymidine nucleotide in the helix junction loop region and phenylalanine 84 of the PDGF-B chain. Representative minimal DNA ligands inhibit the binding of 125I-PDGF-BB but not of 125I-PDGF-AA to PDGF alpha- or beta-receptors expressed in porcine aortic endothelial (PAE) cells in a concentration-dependent manner with half-maximal effects of approximately 1 nM. The same ligands also exhibit a similar inhibitory effect on PDGF-BB-dependent [3H]thymidine incorporation in PAE cells expressing the PDGF beta-receptors. These DNA ligands represent a novel class of specific and potent antagonists of PDGF-BB and, by inference, PDGF-AB.
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