ABSTRACT
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.
Subject(s)
Azacitidine/pharmacology , DNA, Viral/genetics , Inclusion Bodies, Viral/physiology , Teratoma/physiopathology , Animals , Cell Differentiation , Cytarabine/pharmacology , Gene Expression Regulation/drug effects , Methylation , Mice , RNA, Viral/geneticsABSTRACT
5-Azacytidine activates the production of intracisternal A particles (IAPs) in mouse Ki-BALB cell line as ascertained by electron microscopy scanning and numeration. Efficiency of the activation is higher than that obtained with iododeoxyuridine. The increase in particle production is concentration and time dependent. The results obtained in our system correlate the high IAP expression after drug treatment with a demethylation of IAP-related genes sequences.
Subject(s)
Azacitidine/pharmacology , Retroviridae/growth & development , Virus Activation/drug effects , Animals , Cell Line , Cell Transformation, Viral , DNA, Viral/metabolism , Dose-Response Relationship, Drug , Idoxuridine/pharmacology , Kirsten murine sarcoma virus/physiology , Methylation , Mice , Time FactorsABSTRACT
Two main intracisternal-A-particle-specific RNA species (29 to 30S and 35 to 36S) are variably expressed in particle-producing and particle-nonproducing murine teratocarcinoma cell lines. An analysis of DNA methylation patterns after hybridization with an intracisternal-A-particle-specific probe showed an apparent direct correlation between DNA methylation and RNA expression. However, when the methylation assay was performed on the excised intracisternal A particle genes in one of the particle-rich cell lines (PCC6), some undermethylated sequences were detectable. These results are consistent with the concept that only few of the genes are transcriptionally active.
Subject(s)
DNA, Viral/analysis , Gene Expression Regulation , RNA, Viral/analysis , Retroviridae/genetics , Animals , Cell Line , Genes, Viral , Methylation , Mice , Retroviridae/metabolism , TeratomaABSTRACT
Undifferentiated teratocarcinoma cells express sixfold-higher levels of endogenous xenotropic type C virus-related RNA than differentiated cells. Three species of polyadenylated viral RNA (35S, 24S, and 14S) have been identified in the undifferentiated teratocarcinoma cells. Paradoxically, neither viral particles nor viral proteins have been detected in these cells.
