Abstract
The relationship between DNA methylation and the expression of the gamma- and beta-casein genes was investigated in both expressing and nonexpressing tissues and in isolated tumor cell subpopulations displaying differential casein gene expression. MspI/HpaII digestions of DNA isolated from liver, a totally nonexpressing tissue, indicated that specific sites of hypermethylation existed in these genes as compared to the DNA isolated from casein-producing lactating mammary gland. The positions of these sites were mapped in the gamma-casein gene by comparing total genomic DNA Southern blots to the restriction digests of several overlapping phage clones constituting the gamma-casein gene. In contrast, the methylation status of the HhaI sites in the gamma-casein gene was found to be invariant regardless of the expression status of the gene. The inverse correlation between the hypermethylation of certain MspI/HpaII restriction sites in the casein genes and their potential expressibility was further substantiated by studies in 7,12-dimethylbenz(a)anthracene- and N-nitrosomethylurea-induced mammary carcinomas, which have an attenuated casein gene expression, and in cell subpopulations isolated from the 7,12-dimethylbenz(a)-anthracene tumor which were either depleted or enriched in casein-producing cells. Analysis of total tumor DNAs indicated that the casein genes were hypermethylated at the same sites observed in liver. However, a very faint hybridization signal was observed in the HpaII digests, suggesting cell-specific methylation differences. We have confirmed the hypomethylation of at least two of these MspI/HpaII sites within the subpopulation containing the casein-producing cells at a level consistent with the relative enrichment in that fraction. These results demonstrate differential site-specific casein gene methylation not only between tissues but also between cell subpopulations within a single tissue.
Highlights
The relationshipbetween DNA methylation and the correlation
7,12-dimethylbenz(a)anthracene-and N-nitrosome- in the relative proportion of various cell types thatmay occur thylurea-induced mammary carcinomas, which have during development, e.g. between virgin, pregnant, and lacan attenuated casein gene expression, and in cell sub- tating tissue
T-Casein Gene Methylation Patterns-Casein gene methylation wasexamined initially innonexpressing uersus expressing tissues both to determine if a relationship existed between DNA methylation and casein gene expression andto map the positions of potential methylation sites
Summary
T-Casein Gene Methylation Patterns-Casein gene methylation wasexamined initially innonexpressing uersus expressing tissues both to determine if a relationship existed between DNA methylation and casein gene expression andto map the positions of potential methylation sites. 2, the EcoRIIHhaI methylation pattern was identical for the estingly, two bands with weaker hybridization signals at 13 y-casein gene in all four tissues, and fragments of 10.5 and and 5.3 kb were observed only in the MspI digests in these. A faint compared to the total DNdAigestions indicated that threeof signal was observed a t 6.5 kb in the HpaII digests which was the HhaI sitesin the y-casein gene were methylated and one notdetectedintheMspI digests. This mayhave possibly was unmethylated.Thepattern of HhaImethylation was, arisen from an external cytosine methylation 5i’n-CtChGe G-.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
