Figure 3: The expression of EGS RNAs in cultured cells. Northern analyses were carried out using nuclear RNA fractions isolated from parental PM1 cells (—, lanes 4 and 8) and a cloned cell line that expressed C2 (lanes 1 and 5), C1 (lanes 2 and 6), and TK1 (lanes 3 and 7). Equal amounts of each RNA sample (30 μg) were separated on 2% agarose gels that contained formaldehyde, transferred to nitrocellulose membranes, and hybridized to a -radiolabeled probe that contained the DNA sequence coding for EGS C1 (lanes 1–4) or H1 RNA (lanes 5–8), the RNA subunit of human RNase P and a nuclear RNA [15]. The hybridized products corresponding to the full-length retroviral transcripts (~6 kb), transcribed from the LTR promoter, are at the top of the gel and are not shown.