Minor serine tRNA containing anticodon NCA (C4 RNA) from human and mouse cells.

The nucleotide sequence of C4 RNA, one of the "4.5S RNAs" of HeLa cells, was determined. This RNA consists of 90 nucleotides containing C-C-A at its 3'-terminus. The sequence can be drawn to form a clover-leaf structure with several unusual features and with anticodon NCA. The short term labeled molecule contains triphosphates at its 5'-terminus, whereas the mature molecule contains only monophosphate. Therefore, there must be no precursor nucleotide at the 5'-end in the primary transcript of this tRNA. Mouse cells also contain C4 RNA. Only one base exchange was observed in the extra arm in human and mouse C4 RNAs. The molecule purified from mouse liver showed serine acceptor ability.