Transcriptional activity of globin genes in uninducible variants of Friend leukemic cells.

Transcriptional activity of globin genes in inducible and uninducible Friend leukemic cells was studied by two different approaches in an attempt to identify the biochemical basis for the loss of inducibility. (1) Nuclei were isolated, and transcripts synthesized endogenously were purified by the Hg-UTP/sulfhydryl-Sepharose method. Globin mRNA sequences were quantitated by hybridization with [32P]globin cDNA. The results showed that the transcription of globin genes was stimulated in DMSO-treated inducible cell nuclei, whereas there was no activation of globin gene transcription in nuclei of uninducible variants cultured with DMSO. (2) Nuclei were prepared from inducible and uninducible Friend cells cultured in the presence or absence of DMSO, and were then subjected to limited digestion with DNase I. DNA was isolated from the nuclei after about 10% of total DNA had become acid-soluble, and was hybridized with globin cDNA. Globin genes either in inducible or in uninducible Friend cells were specifically susceptible to DNase I irrespective of the addition of inducer. From these studies, it was concluded that globin genes of uninducible Friend cells retained the "active conformation" but were not actively transcribed even in the presence of inducers.