MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford University, Oxford OX3 9DS, United Kingdom.
Genome Res. 2010 Aug;20(8):1064-83. doi: 10.1101/gr.104935.110. Epub 2010 Jun 21.
Coordination of cellular processes through the establishment of tissue-specific gene expression programs is essential for lineage maturation. The basic helix-loop-helix hemopoietic transcriptional regulator TAL1 (formerly SCL) is required for terminal differentiation of red blood cells. To gain insight into TAL1 function and mechanisms of action in erythropoiesis, we performed ChIP-sequencing and gene expression analyses from primary fetal liver erythroid cells. We show that TAL1 coordinates expression of genes in most known red cell-specific processes. The majority of TAL1's genomic targets require direct DNA-binding activity. However, one-fifth of TAL1's target sequences, mainly among those showing high affinity for TAL1, can recruit the factor independently of its DNA binding activity. An unbiased DNA motif search of sequences bound by TAL1 identified CAGNTG as TAL1-preferred E-box motif in erythroid cells. Novel motifs were also characterized that may help distinguish activated from repressed genes and suggest a new mechanism by which TAL1 may be recruited to DNA. Finally, analysis of recruitment of GATA1, a protein partner of TAL1, to sequences occupied by TAL1 suggests that TAL1's binding is necessary prior or simultaneous to that of GATA1. This work provides the framework to study regulatory networks leading to erythroid terminal maturation and to model mechanisms of action of tissue-specific transcription factors.
细胞过程的协调是通过建立组织特异性基因表达程序来实现的，这对于谱系成熟至关重要。造血转录调节因子 TAL1（以前称为 SCL）是红细胞终末分化所必需的。为了深入了解 TAL1 在造血中的功能和作用机制，我们对原代胎儿肝脏红细胞进行了 ChIP-seq 测序和基因表达分析。我们表明，TAL1 协调大多数已知的红细胞特异性过程中的基因表达。TAL1 的大多数基因组靶标需要直接的 DNA 结合活性。然而，TAL1 的五分之一靶序列，主要是那些与 TAL1 具有高亲和力的靶序列，可以在不依赖其 DNA 结合活性的情况下募集该因子。对 TAL1 结合的序列进行无偏 DNA 基序搜索，鉴定出 CAGNTG 是红细胞中 TAL1 优先的 E 盒基序。还鉴定出了新的基序，这可能有助于区分激活和抑制基因，并提出 TAL1 可能被招募到 DNA 的新机制。最后，对 TAL1 蛋白伴侣 GATA1 募集到 TAL1 占据的序列的分析表明，TAL1 的结合是在 GATA1 之前或同时发生的。这项工作为研究导致红细胞终末成熟的调控网络以及模拟组织特异性转录因子作用机制提供了框架。
