Visualization of mouse DNA transcriptional complexes in mouse kidney cells infected with SV 40 virus

Electron microscopic studies of transcribed cellular deoxynucleoprotein (DNP) fibers from mouse kidney cells abortively infected with Simian Virus 40 (SV 40) revealed two types of transcriptional complexes. Tandemly repeating units representing ribosomal transcriptional events, although few in number because of the procedure employed, clearly confirmed results of other techniques which revealed the unusually long length of the untranscribed spacer intercepts in mouse nucleolar chromatin. In non-nucleolar arrays the density of the ribonucleoprotein (RNP) fibrils varied, as did the length and configuration of the associated DNP fibers. A statistical correlation between a "smooth" appearance of a transcribed portion of a DNP fiber and a high density of nascent RNP fibrils was observed.