Figure 4.
HAC1 intron is associated with polysomes in the HA-AtRLG1 strain. Distribution of HAC1 RNA species was examined by polysome analysis. Extracts from HA-ScRLG1 cells (A and C) and HA-AtRLG1[M74] cells (B and D) cultured in the absence (A and B, −Tm) or the presence (C and D, +Tm) of 2.0 μg/ml Tm were subjected to 10–50% sucrose density gradient ultracentrifugation. Fractions were collected from the top (left) to the bottom (right). In each set of three panels, the top, middle, and bottom panels represent A260 trace, HAC1 RNAs, and ACT1 RNA, respectively. In the top panel of A, peak assignments are shown. In the middle panel, positions of HAC1 RNA species were indicated in the right. Amounts of HAC1-related RNAs in the sucrose gradient fractions of HA-AtRLG1 extracts from control (E) or Tm-treated (F) cells were compared with standard RNAs transcribed in vitro. In the bottom panel, Northern signals of HAC1u mRNA (□), HCA1i mRNA (▩) and HAC1 intron (■) were quantified and expressed in arbitrary units. L, cell extract; Std, 0.22 fmol each of HAC1u mRNA, HAC1i mRNA, and HAC1 intron.