Institute of Physiological Chemistry, Ulm University, 89081 Ulm, Germany.
Institute of Biophysics, Ulm University, 89081 Ulm, Germany.
Proc Natl Acad Sci U S A. 2019 Jan 15;116(3):880-889. doi: 10.1073/pnas.1812734116. Epub 2018 Dec 31.
Serum response factor (SRF) mediates immediate early gene (IEG) and cytoskeletal gene expression programs in almost any cell type. So far, SRF transcriptional dynamics have not been investigated at single-molecule resolution. We provide a study of single Halo-tagged SRF molecules in fibroblasts and primary neurons. In both cell types, individual binding events of SRF molecules segregated into three chromatin residence time regimes, short, intermediate, and long binding, indicating a cell type-independent SRF property. The chromatin residence time of the long bound fraction was up to 1 min in quiescent cells and significantly increased upon stimulation. Stimulation also enhanced the long bound SRF fraction at specific timepoints (20 and 60 min) in both cell types. These peaks correlated with activation of the SRF cofactors MRTF-A and MRTF-B (myocardin-related transcription factors). Interference with signaling pathways and cofactors demonstrated modulation of SRF chromatin occupancy by actin signaling, MAP kinases, and MRTFs.
血清应答因子 (SRF) 介导几乎任何细胞类型中的即刻早期基因 (IEG) 和细胞骨架基因表达程序。到目前为止，尚未在单分子分辨率下研究 SRF 的转录动力学。我们对成纤维细胞和原代神经元中的单个 Halo 标记的 SRF 分子进行了研究。在这两种细胞类型中，SRF 分子的单个结合事件分为三个染色质居留时间区，短、中、长结合，表明 SRF 具有细胞类型独立性。在静止细胞中，长结合部分的染色质居留时间长达 1 分钟，在受到刺激后显著增加。刺激也会在两种细胞类型的特定时间点（20 和 60 分钟）增加长结合的 SRF 部分。这些峰与 SRF 辅助因子 MRTF-A 和 MRTF-B（心肌相关转录因子）的激活相关。干扰信号通路和辅助因子表明，肌动蛋白信号、MAP 激酶和 MRTFs 调节 SRF 染色质占有率。
