Wang Jin-Yu, Wang Qi, Peng Ye-Xiang, Jiang Lu-Guang, Lu Zi-Zheng, Zheng Lei-Ming, Li Xiao-Han, Liu Juan, Long Jin-Cheng, Liu Jing-Han, He Yan
Key Laboratory of Seed Innovation, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
State Key Laboratory of Maize Bio-Breeding, National Maize Improvement Center of China, China Agricultural University, Beijing 100094, China.
Plant Cell. 2025 Apr 2;37(4). doi: 10.1093/plcell/koaf071.
Transcript elongation controlled by RNA polymerase II (RNAP II) represents a key regulatory event in numerous cellular processes. However, the precise mechanisms underlying the regulation of RNAP II distribution and progression in plants remain largely elusive. Here, we positionally cloned the causal mutation in the defective kernel 59 (dek59) maize (Zea mays) mutant and demonstrated that Dek59 encodes Structure-Specific Recognition Protein 1 (ZmSSRP1), a subunit of the FAcilitates Chromatin Transcription (FACT) complex that regulates RNAP II. Using genome-wide mapping assays, we determined that ZmSSRP1-binding sites co-localize with those of RNAP II phosphorylated at its serine 2 residue (Ser2P) and are highly enriched within actively transcribed genes. Mutation of ZmSSRP1 resulted in Ser2P accumulation around the +1 nucleosome of genes, affecting gene expression in a gene length-dependent manner. The reduced amount of RNAP II in the dek59 mutant was rescued to wild-type-like levels by inhibiting the proteasome, indicating that arrested RNAP II degradation is proteasome-dependent. These findings reveal the indispensable role of ZmSSRP1 in regulating RNAP II-mediated transcription, which is critical for the proper expression of thousands of genes during maize seed development.
由RNA聚合酶II（RNAP II）控制的转录延伸是众多细胞过程中的关键调控事件。然而，植物中RNAP II分布和进程调控的精确机制在很大程度上仍不清楚。在这里，我们通过定位克隆了有缺陷的籽粒59（dek59）玉米（Zea mays）突变体中的因果突变，并证明Dek59编码结构特异性识别蛋白1（ZmSSRP1），它是调节RNAP II的染色质转录促进因子（FACT）复合物的一个亚基。通过全基因组定位分析，我们确定ZmSSRP1结合位点与在其丝氨酸2残基（Ser2P）处磷酸化的RNAP II的结合位点共定位，并且在活跃转录的基因中高度富集。ZmSSRP1的突变导致基因+1核小体周围Ser2P积累，以基因长度依赖的方式影响基因表达。通过抑制蛋白酶体，dek59突变体中减少的RNAP II量恢复到野生型水平，这表明停滞的RNAP II降解是蛋白酶体依赖性的。这些发现揭示了ZmSSRP1在调节RNAP II介导的转录中的不可或缺的作用，这对于玉米种子发育过程中成千上万个基因的正确表达至关重要。
