Pattern of methylation of two genes coding for housekeeping functions

Area of Science:

• Molecular Biology
• Genetics
• Epigenetics

Background:

• DNA methylation is a key epigenetic mechanism influencing gene expression.
• Tissue-specific methylation patterns are common for many genes.
• The adenine phosphoribosyl-transferase (aprt) and dihydrofolate reductase (dhfr) genes are crucial for nucleotide biosynthesis.

Purpose of the Study:

• To analyze DNA methylation site distribution in the Chinese hamster aprt gene.
• To investigate methylation patterns of the hamster aprt and mouse dihydrofolate reductase (dhfr) genes.
• To determine the relationship between methylation and gene expression, particularly for aprt.

Main Methods:

• Utilized CpG restriction enzymes to analyze methylation patterns.
• Compared methylation status in various somatic tissues and sperm DNA.
• Examined the 5'-end region and overall gene body methylation.

Main Results:

• Both aprt and dhfr genes exhibited complete unmethylation at their 5'-ends and heavy methylation in the gene body.
• The hamster aprt gene's expression is inhibited by DNA methylation in vivo.
• Methylation patterns for both genes were consistent across sperm and somatic tissues, unlike tissue-specific genes.

Conclusions:

• 5' undermethylation of the aprt gene appears necessary for its expression.
• The conserved methylation pattern suggests aprt and dhfr are constitutively expressed housekeeping genes.
• Methylation patterns in sperm reflect general cellular methylation, not tissue-specific regulation for these genes.