Abstract
Seminal vesicle secretory protein IV (SVS IV) is perhaps the most abundant protein made by the epithelial cells of the rat seminal vesicle. In this report, we have asked whether the methylation of its gene correlates with its tissue-specific pattern of expression. Using methylation-sensitive restriction endonucleases HpaII and AvaI, we could examine seven potential methylation sites in or near the gene. All seven sites were largely unmethylated in the seminal vesicle, while in most nonexpressing organs, all sites were heavily modified. The correlation of demethylation with expression was broken by finding that both ventral prostate and coagulating gland (anterior prostate) DNA showed the same demethylation pattern seen for the seminal vesicle. SVS IV protein has not been reported in either of these two organs, and we could not detect mature SVS IV message in prostate RNA or SVS IV transcription by in vitro incubation of prostate nuclei. We conclude that demethylation of the SVS IV gene accompanies the differentiation of several androgen-dependent sex accessory glands but confirm that demethylation per se is not a sufficient signal to bring about gene transcription.
Highlights
From the Chemistry Department and the Biochemistry Section of the School of Medicine, University of South Carolina, Columbia, South Carolina 29208
To testfor the possible transcription of SVS IV to a precursor that is not converted to stable message, we incubated isolated nuclei from prostate, seminal vesicle, and liver in the presence of [cI-~*P]UTP,isolated RNA, and hybridized it to plasmid DNA containing most of the SVS IV gene immobilized on nitrocellulose filters
While we can be confident that thereis virtually no mature message present, the nuclear transcription assays are less sensitive than the Northern blots, and we might not detect a level of transcription that was less than a few per cent of that found in theseminal vesicle
Summary
We conclude that demethylation of the SVSIV tion, asthe gene is highly demethylated in them aws ell. These gene accompanies thdeifferentiationof several andro- results were unexpected in light of arecent study of the gen-dependent sex accessory glands but confirm that methylation of the prostatic steroid-binding protein genes, demethylationper se is not a sufficient signal to bring which are expressed only in the prostate and are demethylated about gene transcription. 5-Methylcytosine is the only modified base found in significant amountsin vertebrate DNA. It occurs almost exclusively in the dinucleotide 5”CG and is proposed to play a role in regulating gene expression (for review, see Ref. 1-3). The first studies to employ this approach lead to thegeneralization that genes are sparsely methylated in tissues where they are expressed
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