CpG islands are important in the protection of adjacent housekeeping genes from de novo DNA methylation and for keeping them in a transcriptionally active state. However, little is known about their capacity to protect heterologous genes and assure position-independent transcription of adjacent transgenes or retroviral vectors. To tackle this question, we have used the mouse aprt CpG island to flank a Rous sarcoma virus (RSV)-derived reporter vector and followed the transcriptional activity of integrated vectors. RSV is an avian retrovirus which does not replicate in mammalian cells because of several blocks at all levels of the replication cycle. Here we show that our RSV-derived reporter proviruses linked to the mouse aprt gene CpG island remain undermethylated and keep their transcriptional activity after stable transfection into both avian and nonpermissive mammalian cells. This effect is most likely caused by the protection from de novo methylation provided by the CpG island and not by enhancement of the promoter strength. Our results are consistent with previous finding of CpG islands in proximity to active but not inactive proviruses and support further investigation of the protection of the gene transfer vectors from DNA methylation.

• MeSH
• Adenine Phosphoribosyltransferase genetics   MeSH
• Cell Line virology   MeSH
• CpG Islands * MeSH
• Defective Viruses genetics   MeSH
• DNA, Viral chemistry   genetics   MeSH
• DNA (Cytosine-5-)-Methyltransferases metabolism   MeSH
• Sarcoma, Experimental genetics   virology   MeSH
• Fibroblasts virology   MeSH
• Transcription, Genetic * MeSH
• Genetic Vectors genetics   physiology   MeSH
• Virus Integration MeSH
• Terminal Repeat Sequences MeSH
• Cricetinae MeSH
• Mesocricetus MeSH
• Chick Embryo MeSH
• DNA Methylation MeSH
• Mice MeSH
• Proviruses genetics   MeSH
• Gene Expression Regulation, Viral * MeSH
• Virus Replication MeSH
• Genes, Reporter MeSH
• Gene Silencing * MeSH
• Avian Sarcoma Viruses genetics   physiology   MeSH
• Animals MeSH
• Check Tag
• Cricetinae MeSH
• Chick Embryo MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Comparative Study MeSH
• Names of Substances
• Adenine Phosphoribosyltransferase MeSH
• DNA, Viral MeSH
• DNA (Cytosine-5-)-Methyltransferases MeSH