Cells on plates either grown to confluency or subconfluent monolayers were washed three times with Kern-matrix buffer (KM buffer). For the first extraction, add (2 ml/plate) KM buffer containing 1% nonident P40 (NP40), 1 mM ethyleneglycol —bis-(β-Aminoethyl ether)N,N’-tetraacetic acid (EGTA), and 5 mM dithiothreitol (DTT). Add another 4 ml buffer and incubate on ice for 30 min. After the first extraction, cells on the plates were washed three times with KM buffer and incubated for 15 min at 30^oC with 50 µg/ml of deoxyribonuclease I (DNase I) in KM buffer. After removal of this extract, KM buffer containing 2 M NaCl, 1 mM EGTA, and 5 mM DTT was added and incubation was for 30 min in the cold. Then structures were washed three times with KM buffer and incubated for 30 min at 37^oC with 50 µg/ml each of DNase I and ribonuclease A (RNase A) in KM buffer.

Staufenbiel M and Deppert W (1984) Preparation of Nuclear Matrices from cultured cells:subfractionation of nuclei in-situ. J Cell Biol 98:1886-1894.