SBDS is required for ribosomal subunit joining in Dictyostelium. (A-B) Subunit joining defect in SBDS-depleted (sbdS^int(ts)) cells. Polysome profiles of extracts from sbdS^int(ts) compared with wild type cells cultured at (A) the permissive (22°C) or (B) the restrictive (27°C) temperature. Arrows indicate halfmer polysomes. (C-D) SBDS depletion does not alter the ratio of 60S to 40S subunits. Ribosome profiles of extracts from sbdS^int(ts) compared with wild type cells cultured at (C) 22°C and (D) 27°C. The 60S:40S subunit ratios are indicated.