Comment on

• Tet proteins can convert 5-methylcytosine to 5-formylcytosine and 5-carboxylcytosine.

  Ito S, Shen L, Dai Q, Wu SC, Collins LB, Swenberg JA, He C, Zhang Y. Ito S, et al. Science. 2011 Sep 2;333(6047):1300-3. doi: 10.1126/science.1210597. Epub 2011 Jul 21. Science. 2011. PMID: 21778364 Free PMC article.
• Tet-mediated formation of 5-carboxylcytosine and its excision by TDG in mammalian DNA.

  He YF, Li BZ, Li Z, Liu P, Wang Y, Tang Q, Ding J, Jia Y, Chen Z, Li L, Sun Y, Li X, Dai Q, Song CX, Zhang K, He C, Xu GL. He YF, et al. Science. 2011 Sep 2;333(6047):1303-7. doi: 10.1126/science.1210944. Epub 2011 Aug 4. Science. 2011. PMID: 21817016 Free PMC article.