Department of Biochemistry & Molecular Medicine, School of Medicine & Health Sciences, The George Washington University, Washington, District of Columbia, USA.
Department of Genomics & Precision Medicine, School of Medicine & Health Sciences, The George Washington University, Washington, District of Columbia, USA; Center for Genetic Medicine Research, Children's National Hospital, Washington, District of Columbia, USA.
J Biol Chem. 2023 Nov;299(11):105259. doi: 10.1016/j.jbc.2023.105259. Epub 2023 Sep 17.
The four-subunit negative elongation factor (NELF) complex mediates RNA polymerase II (Pol II) pausing at promoter-proximal regions. Ablation of individual NELF subunits destabilizes the NELF complex and causes cell lethality, leading to the prevailing concept that NELF-mediated Pol II pausing is essential for cell proliferation. Using separation-of-function mutations, we show here that NELFB function in cell proliferation can be uncoupled from that in Pol II pausing. NELFB mutants sequestered in the cytoplasm and deprived of NELF nuclear function still support cell proliferation and part of the NELFB-dependent transcriptome. Mechanistically, cytoplasmic NELFB physically and functionally interacts with prosurvival signaling kinases, most notably phosphatidylinositol-3-kinase/AKT. Ectopic expression of membrane-tethered phosphatidylinositol-3-kinase/AKT partially bypasses the role of NELFB in cell proliferation, but not Pol II occupancy. Together, these data expand the current understanding of the physiological impact of Pol II pausing and underscore the multiplicity of the biological functions of individual NELF subunits.
四亚基负延伸因子（NELF）复合物介导 RNA 聚合酶 II（Pol II）在启动子近端区域的暂停。单个 NELF 亚基的缺失会破坏 NELF 复合物的稳定性，并导致细胞死亡，这导致了普遍的观点，即 NELF 介导的 Pol II 暂停对于细胞增殖是必不可少的。使用分离功能突变，我们在这里表明，NELFB 在细胞增殖中的功能可以与其在 Pol II 暂停中的功能解耦。NELFB 突变体被隔离在细胞质中并剥夺了 NELF 的核功能，仍然支持细胞增殖和部分 NELFB 依赖的转录组。从机制上讲，细胞质 NELFB 与存活信号激酶，尤其是磷脂酰肌醇-3-激酶/AKT 进行物理和功能相互作用。膜结合的磷脂酰肌醇-3-激酶/AKT 的异位表达部分绕过了 NELFB 在细胞增殖中的作用，但不影响 Pol II 占有率。综上所述，这些数据扩展了对 Pol II 暂停生理影响的现有认识，并强调了单个 NELF 亚基的多种生物学功能。
