Data_Sheet_1_Messenger RNAs of Yeast Virus-Like Elements Contain Non-templated 5′ Poly(A) Leaders, and Their Expression Is Independent of eIF4E and Pab1.pdf

We employed virus-like elements (VLEs) pGKL1,2 from Kluyveromyces lactis as a model to investigate the previously neglected transcriptome of the broader group of yeast cytoplasmic linear dsDNA VLEs. We performed 5′ and 3′ RACE analyses of all pGKL1,2 mRNAs and found them not 3′ polyadenylated and containing frequently uncapped 5′ poly(A) leaders that are not complementary to VLE genomic DNA. The degree of 5′ capping and/or 5′ mRNA polyadenylation is specific to each gene and is controlled by the corresponding promoter region. The expression of pGKL1,2 transcripts is independent of eIF4E and Pab1 and is enhanced in lsm1Δ and pab1Δ strains. We suggest a model of primitive pGKL1,2 gene expression regulation in which the degree of 5′ mRNA capping and 5′ non-template polyadenylation, together with the presence of negative regulators such as Pab1 and Lsm1, play important roles. Our data also support a hypothesis of a close relationship between yeast linear VLEs and poxviruses.

本研究以乳酸克鲁维酵母（Kluyveromyces lactis）来源的病毒样元件（virus-like elements, VLEs）pGKL1、pGKL2作为模型体系，旨在探究此前被忽略的、更广类群的酵母胞质线性双链DNA病毒样元件的转录组特征。我们对所有pGKL1、pGKL2的mRNA开展了5'端与3'端快速扩增cDNA末端（RACE）分析，结果显示这些mRNA均不具备3'端多腺苷酸化修饰，且普遍带有不与VLE基因组DNA互补的未加帽5'端poly(A)先导序列。进一步研究发现，5'端加帽程度和/或5'端mRNA多腺苷酸化程度因基因特异性而异，并由对应的启动子区域调控。pGKL1、pGKL2转录本的表达不依赖于真核翻译起始因子4E（eIF4E）与poly(A)结合蛋白1（Pab1），且在lsm1Δ与pab1Δ缺失菌株中表达显著增强。我们提出了pGKL1、pGKL2原始基因表达调控模型：mRNA 5'端加帽程度、5'端非模板多腺苷化修饰，以及Pab1、Lsm1等负调控因子的存在，共同在该调控过程中发挥关键作用。此外，本研究数据亦支持“酵母线性VLEs与痘病毒存在密切亲缘关系”的假说。