NUCLEAR NONHISTONE PROTEINS IN MURINE MELANOMA CELLS .2. CHANGES FOLLOWING EXPOSURE TO MSH

[摘要] Murine melanoma cells provide an excellent system for studying the proposed role of nuclear nonhistone proteins (NHP) as regulators of gene expression. Cloudman mouse melanoma cells (S91, NCTC 3960, CCL 53), grown in culture, are normally lightly pigmented, but in the presence of melanocyte stimulating hormone (MSH) show a large increase in melanin content. Cells were grown in medium with and without MSH and labeled with 14C- or 3H-leucine, respectively. Following 48 h of incubation, the cells were harvested, combined and nuclei were isolated. The NHP were extracted from these nuclei in a series of steps which yielded 4 major fractions. Each fraction was further separated on DEAE cellulose columns into a total of 40 subfractions, each of which was electrophoresed on SDS [sodium dodecylsulfate] gels. Each gel was sliced and counted and the 14C/3H ratio was determined for each slice. A number of differences in 14C/3H ratios were observed between NHP isolated from MSH-treated and control cells which reflect changes in the synthesis and/or transport of NHP in MSH-treated cells.