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Fig. 7 Evidence for Ybx1 binding of mRNAs and identification of its associated proteins in the mRNPs. (A) GST pull-down assay for protein partners of Ybx1 in the mRNPs. The GST-Ybx1 fusion protein was incubated with the extracts from PG or PV follicles followed by pull-down with glutathione Sepharose 4B. The proteins pulled down were subject to SDS-PAGE separation and MS analysis. (1) eukaryotic translation initiation factor 4E nuclear import factor 1 (4E-T) (gi|61,806,649); (2) protein associated with topoisomerase II homolog 2 isoform 1 (gi|125,831,101); (3) insulin-like growth factor 2 mRNA binding protein 3 (gi|18,858,571); (4) ATP-dependent RNA helicase DDX6 (DEAD box protein 6) (gi|68,444,623) and RNA-associated protein 55 (RAP55) (gi|157,423,287); (5) Y box binding protein 1 (YB-1) (gi|29,477,111); (6) novel protein containing RNA recognition motifs (a.k.a. RRM, RBD, or RNP domain) (gi|94,732,878) (7) zygote arrest 1 (gi|56,207,255); (8) polyadenylate-binding protein 2 (PABP2) (gi|189,521,749). Asterisk, Ybx1; black arrow, GST-Ybx1 fusion protein (intact and truncated forms); white arrow, GST. (B) RT-PCR analysis for mRNAs in the mRNPs pulled down with GST-Ybx1 fusion protein. gdf9, growth differentiation factor 9; gh, growth hormone; ghr1 and ghr2, growth hormone receptor 1 and 2; igf1 and igf2a, insulin-like growth factor 1 and 2a; igfr1a and igfr1b, insulin-like growth factor receptor 1a and 1b; fsta, follistatin a; bmp2a, bmp2b, bmp4, bmp6 and bmp7, bone morphogenetic protein 2a, 2b, 4, 6 and 7; egf, epidermal growth factor; hbegf, heparin-binding EGF-like growth factor; btc, betacellulin; tgfa, transforming growth factor α.