Analysis of Calf‐Thymus Satellite DNA: Evidence for Specific Methylation of Cytosine in C‐G Sequences

作者：Fritz Gautier, Hans Bünemann, Lutz Grotjahn · 发表于：European Journal of Biochemistry · 年份：1977 · DOI：10.1111/j.1432-1033.1977.tb11869.x · 被引用次数：83 · 研究领域：RNA Interference and Gene Delivery、RNA and protein synthesis mechanisms、Cancer-related gene regulation

Digestion of purified calf tymus satellite I (phi = 1.714 g/cm3) with a series of restriction enzymes shows that modification in this satellite occurs preferentially in the sequence C-G. This was also shown to be the case in the other satellites and in bulk chromosomal calf thymus DNA. Cloning of purified satellite I DNA in Escherichia coli makes sites, previously modified, available for cutting with certain restriction enzymes. All these 'new sites' contain the sequence C-G. High-resolution mass spectros-copy establishes that the satellites contain a low concentration of 5-methylcytosine. This infers that methylation which inhibits retriction enzyme cutting must occur preferentially in the sequence C-G. Hybridization of cRNA of cloned satellite I DNA with the satellites III (phi = 1.706 g/cm3) and IV (phi = 1.710 g/cm3) shows that there is no or little sequence homology between these satellites. Digestion of calf thymus satellite I DNA with endoR. EcoRI and subsequent hybridization studies with the fragments shows two EcoRI fragments in addition to the usual 1400-base-pair EcoRI repeat unit.