Figure 2.

Histone release by salt extraction or amine modification after nuclease digestion. CaSki cells were labeled with [³H]lysine and nuclear matrices prepared by either the high-salt method (lanes 1 and 2) or the sulfo-NHS procedure (lanes 3 and 4). The histones from nuclear fractions were labeled heavily with [³H]lysine and were analyzed by SDS/PAGE and fluorography. Most of each histone was released from the nucleus by HaeIII/PstI digestion and sulfo-NHS treatment (lane 3), whereas less than 10% remained in the nuclear matrix fraction (lane 4). By using the more traditional high-salt method, the histones were released after HaeIII/PstI digestion by application of 0.25M ammonium sulfate (lane 1), leaving little histone protein with the nuclear matrix (lane 2).