Abstract
Total RNAs from four BALB/c mouse tissues, containing mostly non-dividing cells (liver and kidney) or variable proportions of dividing cells (uterus and embryo) were analysed for sequences complementary to 3H-DNA transcripts synthesized from BALB/c endogenous, N- and X-tropic retroviruses. Extensive transcription of virogene information was detected in the tissues examined, but such transcription was found to be mostly limited to the homologous regions of the two virus genomes. No additivity of hybridization values could be detected when RNAs from two different tissues were mixed, which suggests that BALB/c mouse liver, kidney, uterus and embryo transcribe a common set of nucleic acid sequences of the homologous regions of the N- and X-tropic viral genomes, in addition to other sequences of the same region that are specific for individual tissues.