Sequence and organization of 5S RNA genes from the eukaryotic protist Acanthamoeba castellanii

A 5S RNA genomic clone has been isolated from Acanthamoeba castellanii and the sequence of the coding region plus flanking DNA was determined. This clone encodes an RNA whose sequence matches that of 5S RNA from this organism. There is sequence similarity in the 5'-flanking region to other eukaryotic 5S RNA genes which require or are greatly affected by upstream regions for transcriptional activity. The immediate 3'-flanking region has a termination sequence similar to that found in all genes that are transcribed by RNA polymerase III. The 5S RNA genes of A. castellanii are dispersed, which is highly unusual, since the majority of eukaryotic organisms contain 5S genes clustered in tandem repeats. There may be up to 480 genes encoding 5S RNA in each A. castellanii cell.