Lack of a specific ribose methylation at guanosine 17 in Morris hepatoma 5123D tRNASer1IGA.

Tumor transfer RNA's (tRNA's) frequently exhibit alterations in column chromatographic profiles and in base compositions when compared to their normal counterparts. Because such alterations may be involved in the dedifferentiated state of cancer cells, it is of interest to determine their structural basis and functional significance. The recent development of highly sensitive postlabeling methods has now made possible sequence analysis of tRNA's from neoplastic tissues available only in limited amounts. We have determined the nucleotide sequence of Morris hepatoma serine tRNA (anticodon IGA) and compared it with its normal counterpart in rat liver. The tumor serine tRNA was found to lack the ribose methylation of guanosine in position 17 of the dihydrouridine loop present in the liver RNA. This result explains the column chromatographic shifts of Morris hepatoma 5123D seryl-tRNA isoacceptors, suggesting that all seryl-tRNA isoacceptors may lack this modification.