Regulation of intracisternal A particles in mouse teratocarcinoma cells: involvement of DNA methylation in transcriptional control.

The methylation state of Intracisternal A Particle (IAP) genes in mouse teratocarcinoma cell lines has been investigated as an approach to study the regulation of the expression of these particles. Treatment of the cells with the methylation inhibitor 5-azacytidine induces the production of the particles in all the cells; the induction is particularly striking in an embryonal carcinoma cell line which is normally devoid of IAPs. The induction is accompanied by decrease in DNA methylation as demonstrated by using the methylation sensitive isoschizomer enzymes MspI and HpaII. Hypomethylation of the IAP genes correlates with accumulation of IAP, specific polyadenylated RNA reinforcing the hypothesis that methylation plays an important role in the control of IAP expression.