Fig 1: YB-1C also forms ssDNA nucleoprotein filaments, unwinds secondary structures and is compatible with mRNA translation. (A) AFM images of circular ssDNA (M13) complexed with indicated proteins at saturation. M13 ssDNA, 2 nM; SSB, 1 µM; YB-1, 0.5 µM; aa 1–219, 0.7 µM; aa 1–180 (YB-1C), 2 µM. Lower right panel: contour length of ssDNA or mRNA nucleoprotein filaments. N = 10. Blue bar: mean. (B) A DNA construct consisting of two circular ssDNA (1500 and 5000 nt) separated by a dsDNA stalk (300 bp) complexed with either YB-1 or YB-1C. ssDNA, 0.5 nM; YB-1, 0.5 µM; aa 1–180 (YB-1C), 2 µM. (C) Left panel: electrophoretic mobility of mRNA or ssDNA in the presence of different proteins. The presence of YB-1C at saturation decreases EtBr fluorescence of the mRNA band, as observed for ssDNA nucleoprotein filament with Escherichia coli SSB. Right panel: quantification of ethidium fluorescence of three replicates under the same condition. (D) In vitro translation assay in RRL. mRNA was pre-incubated with proteins for 10 min before addition in RRL for 10 min. Note the inhibition of mRNA translation by YB-1 but not by YB-1C. mRNA: 4 nM. Anti-YB-1 and anti-luciferase primary antibodies. Both endogenous and overexpressed YB-1 constructs are recognized by the anti-YB-1 antibody (see also Supplementary Figure S1).