The Nrd1-Nab3-Sen1 (NNS) complex integrates molecular cues to direct termination of noncoding transcription in budding yeast. NNS is positively regulated by histone methylation as well as through Nrd1 binding to the initiating form of RNA PolII. These cues collaborate with Nrd1 and Nab3 binding to target RNA sequences in nascent transcripts through their RRM RNA recognition motifs. In this study, we identify nine lysine residues distributed amongst Nrd1, Nab3 and Sen1 that are methylated, suggesting novel molecular inputs for NNS regulation. We identify mono-methylation of one these residues (Nab3-K363me1) as being partly dependent on the H3K4 methyltransferase, Set1, a known regulator of NNS function. Moreover, the accumulation of Nab3-K363me1 is essentially abolished in strains lacking SET3, a SET domain containing protein that is positively regulated by H3K4 methylation. Nab3-K363 resides within its RRM and physically contacts target RNA. Mutation of Nab3-K363 to arginine (Nab3-K363R) decreases RNA binding of the Nab3 RRM in vitro and causes transcription termination defects and slow growth. These findings identify SET3 as a potential contextual regulator of Nab3 function through its role in methylation of Nab3-K363. Consistent with this hypothesis, we report that SET3 exhibits genetic activation of NAB3 that is observed in a sensitized context.

中文翻译：

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Nab3 RRM域中的关键RNA结合赖氨酸残基经历SET1和SET3响应甲基化。

Nrd1-Nab3-Sen1（NNS）复合体整合了分子线索，以直接终止发芽酵母中非编码转录的终止。NNS由组蛋白甲基化以及通过Nrd1与RNA PolII起始形式的结合而受到正调控。这些提示与Nrd1和Nab3通过其RRM RNA识别基序与新生转录物中的靶RNA序列结合而协同作用。在这项研究中，我们确定甲基化的Nrd1，Nab3和Sen1之间分布的九个赖氨酸残基，表明NNS调节的新型分子输入。我们确定这些残基之一（Nab3-K363me1）的单甲基化部分取决于H3K4甲基转移酶Set1，NNS功能的已知调节剂。此外，在缺少SET3的菌株中，Nab3-K363me1的积累已基本消除，一个SET结构域，该结构域由H3K4甲基化正调控。Nab3-K363驻留在其RRM中，并与靶RNA物理接触。Nab3-K363突变为精氨酸（Nab3-K363R）在体外会降低Nab3 RRM的RNA结合，并导致转录终止缺陷和缓慢的生长。这些发现通过其在Nab3-K363的甲基化中的作用将SET3鉴定为Nab3功能的潜在上下文调节物。与此假设一致，我们报告SET3展示了在致敏的背景下观察到的NAB3的遗传激活。这些发现通过其在Nab3-K363的甲基化中的作用将SET3鉴定为Nab3功能的潜在上下文调节物。与此假设一致，我们报告SET3展示了在致敏的背景下观察到的NAB3的遗传激活。这些发现通过其在Nab3-K363的甲基化中的作用将SET3鉴定为Nab3功能的潜在上下文调节物。与此假设一致，我们报告SET3展示了在致敏的背景下观察到的NAB3的遗传激活。