A variant gene and a pseudogene for human 5S RNA are transcriptionally active in vitro.

Screening of a human genomic DNA library with ribosomal 5S RNA yielded a variant 5S rRNA gene (pH5S1) and a pseudogene lacking the first 9 bp and the last 33 bp (pH5S2). Sequence analysis revealed that both genes contain several mutations in their coding region as compared to human 5S rRNA; however, their intragenic promoters are highly conserved. Both genes are transcribed in a homologous HeLa cell S100 extract. pH5S1 gives rise to a 5S-sized product, whereas the two pH5S2-derived RNAs are about 220 and 240 nucleotides long. pH5S1 is transcribed more efficiently than pH5S2; however, its ability to form a stable preinitiation complex is impaired.