Pseudouridylic modification of a 6S RNA transcribed in vitro from highly repetitive and transcribable (Hirt) sequences of salmon total DNA.

Salmon total DNA was transcribed in a HeLa cell extract, and it was found that a distinct 6S RNA is transcribed by RNA polymerase III. By analogy with a 6S RNA transcribed from mouse total DNA in vitro, which we demonstrated to be the transcripts from type 2 Alu family (Sakamoto et al. (1984) Mol Gen Genet 194:1-6), the genes for the 6S RNA in the salmon genome are presumed to be reiterated in at least 10(4)-10(5) copies and to be dispersed among the genome. A fingerprint analysis showed that the nucleotide sequences of the genes for the 6S RNA are extensively conserved. Furthermore, we demonstrated that at least two positions in the 6S RNA are modified in vitro to pseudouridylic acid. The pseudouridylic acid residues are located in specific oligonucleotides and each of the modified nucleotides amounts to 0.5 to 1.0 mol per mol of RNA. The relationship between salmon highly repetitive and transcribable (Hirt) sequences and rodent type 2 Alu family, and the significance of the pseudouridylic modification in relation to the functional role of these sequences are discussed.