The Regulator of Chromosome Condensation protein (RCC1) is located in both the soluble and inclusion body (IB) fractions of the whole cell lysate when expressed in Escherichia coli BL21 (pLysS) at temperatures below 30 degrees C. When bacterial growth was carried out at 20 degrees C, the majority of the RCC1 remained soluble up to 5.5 h postinduction. When the temperature was raised to 25 degrees C, RCC1 IB was dominant by 1.5 h postinduction. The shift in RCC1 IB formation with temperature suggests that in addition to increased translation rates, folding and aggregation processes may contribute to RCC1 IB formation at higher temperatures.