Bergès T, Petfalski E, Tollervey D, Hurt E C
EMBL, Heidelberg, Germany.
EMBO J. 1994 Jul 1;13(13):3136-48. doi: 10.1002/j.1460-2075.1994.tb06612.x.
The nucleolar protein fibrillarin (encoded by the NOP1 gene in yeast), is required for many post-transcriptional steps in yeast ribosome synthesis. A screen for mutations showing synthetic lethality with a temperature sensitive nop1-5 allele led to the identification of the NOP77 gene. NOP77 is essential for viability and encodes a nucleolar protein with a predicted molecular weight of 77 kDa. Depletion of NOP77p impairs both the processing and methylation of the pre-rRNA. The processing defect is greatest for the pathway leading to 25S rRNA synthesis, and is distinctly different from that observed for mutations in other nucleolar components. NOP77p contains three canonical RNA recognition motifs (RRMs), suggesting that it is an RNA binding protein. The NOP77 allele which complements the synthetic lethal nop1 strains has an alanine at position 308, predicted to lie in helix alpha 1 of RRM3, whereas the non-complementing nop77-1 allele contains a proline at the corresponding position. We propose that NOP77p mediates specific interactions between NOP1p and the pre-rRNA.
核仁蛋白纤维蛋白原（由酵母中的NOP1基因编码）是酵母核糖体合成中许多转录后步骤所必需的。对与温度敏感的nop1 - 5等位基因表现出合成致死性的突变进行筛选，从而鉴定出了NOP77基因。NOP77对细胞活力至关重要，它编码一种预测分子量为77 kDa的核仁蛋白。NOP77p的缺失会损害前体rRNA的加工和甲基化。对于导致25S rRNA合成的途径，加工缺陷最为严重，并且与在其他核仁成分中的突变所观察到的情况明显不同。NOP77p包含三个典型的RNA识别基序（RRMs），表明它是一种RNA结合蛋白。与合成致死的nop1菌株互补的NOP77等位基因在308位有一个丙氨酸，预计位于RRM3的α1螺旋中，而不互补的nop77 - 1等位基因在相应位置含有一个脯氨酸。我们提出NOP77p介导NOP1p与前体rRNA之间的特异性相互作用。
