Evidence that deoxyribonucleic acid sequences flanking the ovalbumin gene are not transcribed

The transcription of DNA sequences flanking the 5' end and 3' end of the ovalbumin gene was examined. First, various restriction endonuclease fragments corresponding to the 5' and 3' regions of the gene isolated and used as hybridization probes to assay for the presence of transcripts corresponding to these different regions in the chick oviduct nuclear RNA. Very little, if any, of the transcripts corresponding to sequences flanking the 5' and 3' structural sequences of the ovalbumin gene was detected in the steady-state nuclear RNA. Second, RNA was pulse labeled either in isolated nuclei or in an oviduct tissue suspension system and hybridized to DNA filters containing purified fragments of various 5'- and 3'-flanking regions. Our results again demonstrated that RNA was not synthesized from the 5'- and 3'-flanking regions surrounding the gene. Taken together, these results are consistent with the postulate that flanking DNA sequences are not transcribed and that the largest RNA species detected in the nuclear RNA are the initial transcripts.