Nucleoproteins derived from subnuclear RNA polymerase complexes of metastatic large-cell lymphoma cells possess transcription activities and regulatory properties in vitro

Intact nuclei derived from poorly or highly liver‐metastatic murine large‐cell lymphoma cell line RAW117 were digested to discrete subchromatin deoxyribonucleoprotein/ribonucleoprotein (DNP/RNP) complexes with Msp‐1. The DNP/RNP complexes were composed of DNP/RNPs which were derived from the DNP/RNP complexes by incubation in the presence or absence of DNase‐1 and subsequent isolation by two‐dimensional [isoelectric focusing/sodium dodecylsulfate (SDS)] polyacrylamide gel electrophoresis (PAGE), electroelution from the gel, and removal of SDS. Approximately 450 DNP/RNPs in the two‐dimensional gels corresponding to discrete spots or in some cases streaks were analyzed for the presence of v‐abl, p53, c‐neu, c‐H‐ras, β‐casein, 18s rDNA, and μ‐chain immunoglobulin genes using a hybridization technique. Ten DNP/RNP complexes contained tightly associated p53 DNA, whereas six contained c‐ or v‐abl, four contained μ‐chain gene, two contained c‐H‐ras, one contained dot‐blot β‐casein, two contained 18s rDNA, and c‐neu was found in one of the DNP/RNPs. The DNP/RNPs were also analyzed for in vitro RNA polymerase and primase activities. To assess the potential transcription abilities of the isolated DNP/RNPs, individual DNP/RNPs or DNP/RNP mixtures (reconstituted after SDS‐PAGE separation) were examined for RNA polymerase initiation and synthesis. When RNA products were formed, these were purified by extracellulose chromatography and used as back‐hybridization probes for the genes of interest. The RNA products were also analyzed by RNA gel electrophoresis. RNA formation was inhibitable by actinomycin D, and the RNAs formed ranged in size from ∼ 80 kbp to ∼ 1 kbp. By mixing various DNP/RNP complexes together, different patterns of RNA synthesis were found. For example, one DNP/RNP of Mr ∼ 140,000, isoelectric point(pl) ∼ 5.8 synthesized a high molecular weight RNA in vitro that hybridized with β‐casein cDNA, but β‐casein is not expressed in RAW117 cells, suggesting that the silencing of the β‐casein gene was negated by isolation of the DNP/RNP. Mixing this DNP/RNP with two other specific DNP/RNPs again inhibited the synthesis of β‐casein RNA, suggesting that interactions between DNP/RNP complexes can result in differential RNA expression or regulation of RNA polymerases in vitro. © 1992 Wiley‐Liss, Inc.