Salvage of the modified nucleoside ribothymidine in cultured hamster embryo cells.

RNA turnover in hamster embryo cells results in the release of ribothymidine, a methylated nucleoside formed only on intact RNA. [methyl-3H]Methionine ribothymidine polyphosphates and deoxyribothymidine polyphosphates are found in approximately equivalent amounts in the acid-soluble pool of hamster embryo cells. This observation is consistent with prior unexplained observations, in intact animals, that the methyl group of S-adenosyl methionine can be used for deoxythymidine synthesis, This is the only modified ribonucleoside known to be salvaged through pathways in normal cells. Several possible pathways for salvage were investigated.