Tho2-mediated escort of Nrd1 regulates gene expression for lifespan maintenance. Tho2-mediated escort of Nrd1 regulates gene expression for lifespan maintenance

The relationship between aging and RNA biogenesis and trafficking is attracting growing interest, yet the precise mechanisms are unknown. The THO complex is crucial for mRNA cotranscriptional maturation and export. Herein, we report that the THO complex is closely linked to maintaining a normal lifespan. Deficiencies in Hpr1 and Tho2, components of the THO complex, reduced replicative lifespan (RLS) and are linked to a novel Sir2-independent RLS control pathway. Although transcript sequestration in hpr1Δ or tho2Δ mutants was countered by exosome component Rrp6, loss of this failed to mitigate RLS defects in hpr1Δ. However, RLS impairment in tho2Δ was counteracted by Nrd1-specific mutants that interacted with Rrp6. This effect relied on the interaction of Nrd1, a transcriptional regulator of aging-related genes, including ribosome biogenesis or RNA metabolism genes, with RNA polymerase II. Nrd1 overexpression reduced RLS in a Tho2-dependent pathway. Intriguingly, THO2 deletion mirrored Nrd1 overexpression effects by inducing arbitrary Nrd1 chromatin binding. Taken together, these findings underscore the importance of Tho2-mediated Nrd1 escorting in maintaining a normal lifespan by transcriptional regulation of aging-related genes. Overall design: Yeast strains WT and tho2Δ were grown in 5 mL of YPD until mid-log phase. mRNA profiles of them were generated by sequencing, in duplicate, using Illumina NovaSeq 6000.

衰老与RNA生物发生及转运之间的关联正受到越来越多的关注，但其具体调控机制仍未明确。THO复合物（THO complex）在mRNA共转录成熟与输出过程中发挥关键作用。本研究表明，THO复合物与正常寿命的维持密切相关。作为THO复合物的组分，Hpr1与Tho2的缺失会缩短复制型寿命（replicative lifespan，RLS），并与一条新的不依赖Sir2的RLS调控通路相关。尽管外切体复合物组分Rrp6可逆转hpr1Δ或tho2Δ突变体中的转录本滞留现象，但缺失Rrp6无法缓解hpr1Δ菌株的RLS缺陷。然而，tho2Δ菌株的RLS损伤可被与Rrp6相互作用的Nrd1特异性突变体所逆转。该效应依赖于Nrd1与RNA聚合酶II（RNA polymerase II）的相互作用；Nrd1是一类衰老相关基因（包括核糖体生物发生或RNA代谢相关基因）的转录调控因子。过表达Nrd1会通过依赖Tho2的通路缩短RLS。有趣的是，THO2基因缺失会诱导Nrd1在染色质上的非特异性结合，从而模拟Nrd1过表达的效应。综上，本研究结果凸显了Tho2介导的Nrd1护送作用，通过调控衰老相关基因的转录以维持正常寿命的重要性。
实验设计：将野生型（wild type，WT）及tho2Δ酵母菌株在5 mL YPD培养基（酵母提取物蛋白胨葡萄糖培养基，yeast extract peptone dextrose）中培养至对数中期。采用Illumina NovaSeq 6000测序平台对两组样本的mRNA表达谱进行双重复检测。