Schizosaccharomyces pombe Pol II Transcription Elongation Factor ELL Functions as Part of a Rudimentary Super Elongation Complex. Schizosaccharomyces pombe Pol II Transcription Elongation Factor ELL Functions as Part of a Rudimentary Super Elongation Complex

ELL family transcription factors activate the overall rate of RNA polymerase II (Pol II) transcription elongation by binding directly to Pol II and suppressing its tendency to pause. In metazoa, ELL regulates Pol II transcription elongation as part of a large multisubunit complex referred to as the Super Elongation Complex (SEC), which includes P-TEFb and EAF, AF9 or ENL, and an AFF family protein. Although orthologs of ELL and EAF have been identified in lower eukaryotes including S. pombe, it has been unclear whether SEC-like complexes function in lower eukaryotes. In this report, we describe isolation from S. pombe of an ELL-containing complex with features of a rudimentary SEC. This complex includes S. pombe Ell1, Eaf1, and a previously uncharacterized protein we designate Ell1 binding protein 1 (Ebp1), which is distantly related to metazoan AFF family members. Like the metazoan SEC, this S. pombe ELL complex appears to function broadly in Pol II transcription. Interestingly, it appears to have a particularly important role in regulating genes involved in cell separation. Overall design: All experminents were performed in duplicates. For Ell1, Eaf1, and Ebp1 ChIP experiments, ell1Δ, eaf1Δ and ebp1Δ strains were used as controls.

ELL家族转录因子（ELL family transcription factors）可通过直接结合RNA聚合酶II（RNA polymerase II, Pol II）并抑制其暂停倾向，整体提升RNA聚合酶II的转录延伸速率。在多细胞生物中，ELL作为大型多亚基复合物的组分调控Pol II转录延伸，该复合物被称为超级延伸复合物（Super Elongation Complex, SEC），其组分包含P-TEFb、EAF、AF9或ENL，以及AFF家族蛋白。尽管在粟酒裂殖酵母（S. pombe）等低等真核生物中已鉴定出ELL和EAF的直系同源蛋白，但低等真核生物中是否存在类似SEC的复合物仍不明确。本研究报道了从粟酒裂殖酵母中分离得到一种包含ELL的复合物，其具备雏形超级延伸复合物的特征。该复合物由粟酒裂殖酵母Ell1、Eaf1，以及一种此前未被表征的蛋白组成，我们将其命名为Ell1结合蛋白1（Ell1 binding protein 1, Ebp1），该蛋白与多细胞生物的AFF家族成员亲缘关系较远。与多细胞生物的超级延伸复合物类似，该粟酒裂殖酵母ELL复合物似乎广泛参与Pol II转录过程。有趣的是，它在调控细胞分离相关基因方面似乎发挥尤为重要的作用。实验设计：所有实验均重复开展两次。针对Ell1、Eaf1和Ebp1的染色质免疫沉淀（Chromatin Immunoprecipitation, ChIP）实验，分别以ell1Δ、eaf1Δ和ebp1Δ基因敲除菌株作为对照。