Abstract
The organization of the chicken transferrin gene and its surrounding sequences was determined by a comparison of the restriction map of the cloned structural gene (double-stranded cDNA) with the map of the transferrin gene in genomic DNA. This analysis reveals a complex arrangement of the transferrin gene in which structural sequences are interrupted by a minimum of 6 intervening sequences, and span at least 10 kilobases in genomic DNA. Furthermore, comparison of the DNA from individual chickens of the same breed indicates considerable allelic diversity in the restriction sites for Eco RI, HindIII, and Bam HI. Quantitation of the number of transferrin genes by saturation hybridization confirms that both liver and oviduct DNAs contain only 1 transferrin gene/haploid complement, and, in addition, comparison of the restriction patterns obtained with DNA from these two tissues, as well as erythrocyte DNA, does not reveal any difference in the structural organization of the gene. We conclude that the distinct tissue-specific transcriptional regulation of this gene by steroids and iron levels in the oviduct and liver cannot be explained either by a multiplicity of genes or by somatic reorganization of the gene.
Highlights
The organization ofthe chicken transferrin gene and can be modulated quite differently in the two tissues [5]
For its surrounding sequences was determined by a com- example, despite the fact that both the liver and the oviduct parison ofthe restriction m a p of the cloned structural are steroid-responsive tissues, the gene in the oviduct is congene with the m a p of the siderably more sensitive to steroid hormones; following the transferrin gene in genomic DNA
This analysis reveals administration of either estrogen or glucocorticoids, oviduct a complex arrangement othf e transferrin gene in which transferrinmRNA levels increase 10- to 15-fold, whereas structural sequences are interrupted by a minimum of 6 intervening sequences, and span at least 10 kilobases in genomicDNA
Summary
For its surrounding sequences was determined by a com- example, despite the fact that both the liver and the oviduct parison ofthe restriction m a p of the cloned structural are steroid-responsive tissues, the gene in the oviduct is congene (double-strandedcDNA) with the m a p of the siderably more sensitive to steroid hormones; following the transferrin gene in genomic DNA. Haploid chick genome(lo), the length of pBR322 DNA (4359 nucleotides) as determined by sequencing (Il),and thelength of the transferrin sequence inserted into p33R322 (2350 nucleotides) asdetermined bygel electrophoresis and electron microscopy [12] These DNA standards, as well as purified chick liver and oviduct DNAs, were sheared by alkaline digestion (0.3N NaOH at 100°C for 40 min), neutralized, and precipitated with ethanol.
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