The Effect of Spt5p on Transcriptional Directionality [ChIP-seq]

SPT5 is a well-conserved factor which manipulates multiple stages of transcription including promoter-proximal pausing (PPP). Furthermore, recent studies have reported an unidentified increase of antisesne transcripts near promoters in SPT5 mutations. Here, we have identified Spt5p-restricted intragenic antisense transcripts which are in close relationship with sense transcription. The antisense highly-restricted genes have common properties: endogenously strong sense transcription and weak antisense transcription, which is also conserved in humans. We identified that Spt5p depletion reduce H3K36me3 and H3K79me3 and lead to histone hyperacetylation, which might be the intermediate stage to induce antisense transcription. We additionaly found possible termination factors that are involved in the antisense restriction with Spt5p. By unveiling the new role of SPT5 in finely balancing the transcription bidirections, we revealed that transcription machinery can determine the direction cotranscriptionally.SPT5是一类高度保守的转录调控因子，可调控转录的多个阶段，包括启动子近端暂停（promoter-proximal pausing, PPP）。近期有研究报道，在SPT5突变体中，启动子附近的反义转录本出现了未被认知的异常上调。本研究鉴定出一类受SPT5蛋白（Spt5p）限制的基因内反义转录本，其与正义转录存在紧密关联。这类反义转录本表达高度受限的基因具有共同特征：内源性正义转录水平较强，而反义转录水平较弱，该特征在人类中同样保守。我们发现，Spt5p的敲除会降低组蛋白H3赖氨酸36三甲基化（H3K36me3）与组蛋白H3赖氨酸79三甲基化（H3K79me3）的水平，并引发组蛋白高度乙酰化，这可能是诱导反义转录产生的中间环节。此外，本研究还发现了可能与Spt5p共同参与反义转录受限调控的转录终止因子。通过揭示SPT5在精细平衡转录双向调控中的新功能，本研究证实转录机器可在共转录过程中决定转录方向。