Hofmann J, Winckler T, Hanenkamp A, Bukenberger M, Schumann G, Marschalek R, Dingermann T
Institut für Biochemie, Med. Fak., Universität Erlangen-Nürnberg, Germany.
Biochem Biophys Res Commun. 1993 Mar 15;191(2):558-64. doi: 10.1006/bbrc.1993.1254.
In eukaryotes 5S rRNA genes are transcribed by RNA polymerase III. These genes occur in D. discoideum on the ca. 90 copies of an extrachromosomal palindrom together with the other ribosomal RNAs, which are generally transcribed by RNA polymerase I. A 5S rRNA gene has been isolated and its nucleotide sequence as well as the organization of the gene relative to the RNA polymerase I operon has been determined. The sequence of the coding region corresponds exactly to an earlier published 5S rRNA sequence. The genes are located just downstream from the 26S RNA and transcription orientations of the pol I genes and the pol III gene point into the same direction, away from the centromer of the palindrom. The isolated gene appears to be functional since it serves as a specific target for a nuclear protein, most likely TFIIIA. A genomic copy of a 5S rRNA pseudogene has been isolated from the D. discoideum strain V12. This pseudocopy contains nucleotides 52 to 82 of a bona fide 5S rRNA gene with only three mismatches. It resides 78 nucleotides downstream from the glu13(UUC) tRNA gene which in the D. discoideum strain V12 is associated with the retrotransposable element DRE.
在真核生物中，5S核糖体RNA基因由RNA聚合酶III转录。这些基因在盘基网柄菌中存在于约90个拷贝的染色体外回文结构上，与其他核糖体RNA一起，后者通常由RNA聚合酶I转录。一个5S核糖体RNA基因已被分离出来，其核苷酸序列以及该基因相对于RNA聚合酶I操纵子的组织方式已被确定。编码区的序列与先前发表的5S核糖体RNA序列完全一致。这些基因位于26S RNA的下游，RNA聚合酶I基因和RNA聚合酶III基因的转录方向指向同一方向，远离回文结构的着丝粒。分离出的基因似乎具有功能，因为它是一种核蛋白（很可能是TFIIIA）的特异性靶点。一个5S核糖体RNA假基因的基因组拷贝已从盘基网柄菌V12菌株中分离出来。这个假拷贝包含一个真正的5S核糖体RNA基因的第52至82个核苷酸，只有三个错配。它位于glu13（UUC）tRNA基因下游78个核苷酸处，在盘基网柄菌V12菌株中，该tRNA基因与反转录转座元件DRE相关。
