Batts-Young B, Lodish H F
Proc Natl Acad Sci U S A. 1978 Feb;75(2):740-4. doi: 10.1073/pnas.75.2.740.
We present here direct evidence for the preservation of a transcriptional initiation sequence in a eukaryotic rRNA precursor: the 5'-end group for precursor to 17S rRNA (p17S RNA) from Dictyostelium discoideum is identified as the triphosphate residue pppA-. We also show that mature 5S RNA form Dictyostelium bears a different triphosphate residue, pppG-. In contrast, we find no evidence for more than one phosphate at the 5' end of the 25S rRNA precursor (p25S RNA). These observations indicate that synthesis of the large ribosomal RNAs of Dictyostelium begins with the 5'-terminal sequence of the p17S RNA, and that 5S RNA transcription must be initiated independently, despite the close association of the 5S and rRNA coding segments.
我们在此展示了真核生物rRNA前体中转录起始序列得以保留的直接证据：盘基网柄菌17S rRNA前体（p17S RNA）的5'端基团被鉴定为三磷酸残基pppA-。我们还表明，盘基网柄菌的成熟5S RNA带有不同的三磷酸残基pppG-。相比之下，我们没有发现25S rRNA前体（p25S RNA）的5'端有不止一个磷酸的证据。这些观察结果表明，盘基网柄菌的大型核糖体RNA的合成始于p17S RNA的5'端序列，并且尽管5S和rRNA编码区段紧密相连，但5S RNA转录必须独立起始。
