Fig. 1. Identification of KPNB1 RBPs in the sciatic nerve.

(A) Secondary structure predictions of RNA motifs used in RNA affinity chromatography as shown. Secondary structures for MAIL (Motif for Axonal Importin Localization), and mutated GMAIL and IMAIL control motifs, were generated using Mfold (61) with modified bases shown in red. (B) Proteins identified by MS on MAIL versus GMAIL pull-downs from rat axoplasm. Enrichment score (cutoff in red = 0.667) versus peptide count (PC)/molecular weight (MW) shown in log scale (cutoff in red = 0.0004), for details see data S1. (C) WBs for PTBP1 from mouse sciatic nerve (SN) axoplasm after pull-down with MAIL or control RNA motifs. Note that PTBP1 is enriched in the MAIL pull-down while depleted from the supernatant. (D) In vitro binding assay using recombinant PTBP1 or nucleolin (NCL) protein with MAIL, IMAIL or the zipcode motif (ZIP) of β-actin, with detection by WB, shows direct association of PTBP1 protein with the MAIL RNA localization motif of KPNB1.