Figure 6.

In condensing spermatids, H2AL1/L2 are associated with the new nucleoprotein structure identified by MNase digestion. Nucleoprotein structures released from step 12–16 spermatids after MNase digestion were fractionated by ultracentrifugation on a sucrose gradient. DNA fragments and proteins of each collected fraction were analyzed, respectively, by electrophoresis on an agarose gel (DNA) and by Western blot using the appropriate antibodies. A and B correspond to two independent experiments. In B, fractions 3–5 (containing the small fragment [Sm]) and fractions 8–10 (containing the nucleosomal fragment [Nuc]) of the gradient were pooled for Western blots (bottom, lanes 2 and 3) and Coomassie staining (top, lanes 1 and 2) analyses, respectively. To confirm the absence of H3 and H4, the proteins from the small fragment fraction were also loaded in tenfold excess (Western blot [WB], lane 4).