RECOVERY OF NUCLEAR MATRIX ULTRASTRUCTURE OF INTERPHASE CHO CELLS AFTER HEAT-SHOCK

Heat shock induces changes in G(1) CHO cell nuclear matrix (NM) ultras tructure that may be related to heat-induced nuclear protein accumulat ion (Wachsberger and Coss, 1993, J. Cell. Physiol., 155:615-634). The present study quantitates recovery of alterations in NM fine structure in CHO cells heated in G1 and compares structural recovery with recov ery of bulk RNA synthesis and surviving fraction (SF). Morphology of N M preparations was quantified 30 min and 20 hr following heat shock by 1) measurement of the number of fiber anastomosing points per unit ar ea per NM, and 2) measurement of the length of fibers between points o f anastomoses within individual NMs. Architectural recovery was nearly complete within 20 hr in cells heated at 43 degrees C or 45 degrees C with SFs of 0.27 or greater. No recovery of architecture was observed in heated cells with SFs of approximately 0.01 or less. The residual damage to NMs was associated with RNA-containing fiber networks as det ermined by means of RNase gold labeling. Recovery from inhibition of R NA synthesis following heat shock was related to recovery of NM archit ecture. It is suggested that 1) repair of NM architecture does not req uire full recovery of bulk RNA synthesis, and 2) partial or complete i rreversible collapse of the NM may be responsible, in part, for heat-i nduced, interphase cell death. (C) 1994 Wiley-Liss, Inc.