Gu Yue, Jones Amanda E, Yang Wei, Liu Shanrun, Dai Qian, Liu Yudong, Swindle C Scott, Zhou Dewang, Zhang Zhuo, Ryan Thomas M, Townes Tim M, Klug Christopher A, Chen Dongquan, Wang Hengbin
Department of Biochemistry and Molecular Genetics, Stem Cell Institute, University of Alabama at Birmingham, Birmingham, AL 35294;
Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294;
Proc Natl Acad Sci U S A. 2016 Jan 5;113(1):E51-60. doi: 10.1073/pnas.1517041113. Epub 2015 Dec 22.
Epigenetic mechanisms play important regulatory roles in hematopoiesis and hematopoietic stem cell (HSC) function. Subunits of polycomb repressive complex 1 (PRC1), the major histone H2A ubiquitin ligase, are critical for both normal and pathological hematopoiesis; however, it is unclear which of the several counteracting H2A deubiquitinases functions along with PRC1 to control H2A ubiquitination (ubH2A) level and regulates hematopoiesis in vivo. Here we investigated the function of Usp16 in mouse hematopoiesis. Conditional deletion of Usp16 in bone marrow resulted in a significant increase of global ubH2A level and lethality. Usp16 deletion did not change HSC number but was associated with a dramatic reduction of mature and progenitor cell populations, revealing a role in governing HSC lineage commitment. ChIP- and RNA-sequencing studies in HSC and progenitor cells revealed that Usp16 bound to many important hematopoietic regulators and that Usp16 deletion altered the expression of genes in transcription/chromosome organization, immune response, hematopoietic/lymphoid organ development, and myeloid/leukocyte differentiation. The altered gene expression was partly rescued by knockdown of PRC1 subunits, suggesting that Usp16 and PRC1 counterbalance each other to regulate cellular ubH2A level and gene expression in the hematopoietic system. We further discovered that knocking down Cdkn1a (p21cip1), a Usp16 target and regulated gene, rescued the altered cell cycle profile and differentiation defect of Usp16-deleted HSCs. Collectively, these studies identified Usp16 as one of the histone H2A deubiquitinases, which coordinates with the H2A ubiquitin ligase PRC1 to regulate hematopoiesis, and revealed cell cycle regulation by Usp16 as key for HSC differentiation.
表观遗传机制在造血作用和造血干细胞（HSC）功能中发挥着重要的调控作用。多梳抑制复合物1（PRC1）的亚基是主要的组蛋白H2A泛素连接酶，对正常和病理性造血作用均至关重要；然而，目前尚不清楚几种起拮抗作用的H2A去泛素酶中哪一种与PRC1共同作用来控制H2A泛素化（ubH2A）水平并在体内调节造血作用。在此，我们研究了Usp16在小鼠造血作用中的功能。骨髓中Usp16的条件性缺失导致整体ubH2A水平显著升高并造成致死性。Usp16缺失并未改变造血干细胞数量，但与成熟细胞和祖细胞群体的显著减少有关，揭示了其在控制造血干细胞谱系定向分化中的作用。对造血干细胞和祖细胞进行的染色质免疫沉淀及RNA测序研究表明，Usp16与许多重要的造血调节因子结合，且Usp16缺失改变了转录/染色体组织、免疫反应、造血/淋巴器官发育以及髓系/白细胞分化相关基因的表达。敲低PRC1亚基可部分挽救这种基因表达的改变，这表明Usp16和PRC1相互平衡以调节造血系统中的细胞ubH2A水平和基因表达。我们进一步发现，敲低作为Usp16靶标和受调控基因的Cdkn1a（p21cip1）可挽救Usp16缺失的造血干细胞改变的细胞周期谱和分化缺陷。总的来说，这些研究确定Usp16为组蛋白H2A去泛素酶之一，它与H2A泛素连接酶PRC1协同调节造血作用，并揭示了Usp16介导的细胞周期调控是造血干细胞分化的关键。
