Z3, A NOVEL ANTISENSE SNORNA FROM SACCHAROMYCES-CEREVISIAE

Small nucleolar RNA (snoRNA) is one of the most important elements par ticipating in eukaryoric ribosomal biogenesis. The present report desc ribes the results of the identification of a novel snoRNA, Z3, from ye ast S. cerevisiae. Z3 snoRNA is 106 nts in length. It contains box C, D elements and a 13 nt complementarity to 25S rRNA. This antisense seg ment, together with the downstream box D, guides a 2'-O-ribose methyla tion of cytidine acid at position 2956th in yeast 25 S rRNA. 23 snoRNA , encoded by an independent transcribed gene on the chromosome XIII of yeast, possesses the same functional elements responsible for the rRN A methylation site as that of the intron-encoded U35 snoRNA of vertebr ate.