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. 1983 Aug 11;11(15):5131–5145. doi: 10.1093/nar/11.15.5131

Methylation of ribosomal RNA genes in the macronucleus of Tetrahymena thermophila.

E H Blackburn, W C Pan, C C Johnson
PMCID: PMC326242  PMID: 6308573

Abstract

We have investigated the occurrence of methylated adenine residues in the macronuclear ribosomal RNA genes of Tetrahymena thermophila. It has been shown previously that macronuclear DNA, including the palindromic ribosomal RNA genes (rDNA), of Tetrahymena thermophila contains the modified base N-6-methyladenine, but no 5-methylcytosine. Purified rDNA was digested with restriction enzymes Sau 3AI, MboI and DpnI to map the positions and levels of N-6-methyladenine in the sequence 5' GATC 3'. A specific pattern of doubly methylated GATC sequences was found; hemimethylated sites were not detected. The patterns and levels of methylation of these sites did not change significantly in different physiological states. A molecular form of the rDNA found in the newly developing macronucleus and for several generations following the sexual process, conjugation, contained no detectably methylated GATC sites. However, both the bulk macronuclear DNA and palindromic rDNA from the same macronuclei were methylated. Possible roles for N-6-methyladenine in macronuclear DNA are discussed in light of these findings.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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