Figure 3.

Complementation of transcription defect in chromatin from the homozygous mutant cell line KO375 with nuclear extracts of HeLa cells. KO375 and GM1310B cells were prelabeled with [¹⁴C]thymidine, encapsulated, and lysed with 0.5% Triton X-100 for 15 min on ice. The lysed cells were washed several times with PBS and incubated with 50 μg of nuclear extracts prepared from HeLa cells in separate reactions. The transcription measured in the chromatin of KO375 cells without the addition of nuclear extracts served as a control to determine the transcription enhancement by HeLa nuclear extracts. The transcription rate is expressed as [³H]UMP incorporated per 10⁶ cells based on the specific activity of [¹⁴C]thymidine per cell.