Li Q, Zhang M, Duan Z, Stamatoyannopoulos G
School of Medicine, University of Washington, Seattle, Washington, 98195, USA.
Genomics. 1999 Oct 15;61(2):183-93. doi: 10.1006/geno.1999.5954.
The beta-globin locus control region (LCR) is a cis regulatory element that is located in the 5' part of the locus and confers high-level erythroid lineage-specific and position-independent expression of the globin genes. The LCR is composed of five DNase I hypersensitive sites (HSs), four of which are formed in erythroid cells. The function of the 5'-most site, HS5, remains unknown. To gain insights into its function, mouse HS5 was cloned and sequenced. Comparison of the HS5 sequences of mouse, human, and galago revealed two extensively conserved regions, designated HS5A and HS5B. DNase I hypersensitivity mapping revealed that two hypersensitive sites are located within the HS5A region (designated HS5A(major) and HS5A(minor)), and two are located within the HS5B region (HS5B(major), HS5B(minor)). The positions of each of these HSs colocalize with either GATA-1 or Ap1/NF-E2 motifs, suggesting that these protein binding sites are implicated in the formation of HS5. Gel retardation assays indicated that the Ap1/NF-E2 motifs identified in murine HS5A and HS5B interact with NF-E2 or similar proteins. Studies of primary murine cells showed that HS5 is formed in all hemopoietic tissues tested (fetal liver, adult thymus, and spleen), indicating that this HS is not erythroid lineage specific. HS5 was detected in murine brain but not in murine kidney or adult liver, suggesting that this site is not ubiquitous. The presence of GATA-1 and NF-E2 motifs (which are common features of the DNase I hypersensitive sites of the LCR) suggests that the HS5 is organized in a manner similar to that of the other HSs. Taken together, our results suggest that HS5 is an inherent component of the beta-globin locus control region.
β-珠蛋白基因座控制区（LCR）是一种顺式调控元件，位于该基因座的5'端，赋予珠蛋白基因高水平的红系谱系特异性和位置独立表达。LCR由五个DNase I超敏位点（HSs）组成，其中四个在红系细胞中形成。最5'端的位点HS5的功能尚不清楚。为了深入了解其功能，对小鼠HS5进行了克隆和测序。对小鼠、人类和婴猴的HS5序列进行比较，发现了两个广泛保守的区域，分别命名为HS5A和HS5B。DNase I超敏图谱显示，两个超敏位点位于HS5A区域内（分别命名为HS5A（主要）和HS5A（次要）），另外两个位于HS5B区域内（HS5B（主要）、HS5B（次要））。这些HSs中的每一个的位置都与GATA-1或Ap1/NF-E2基序共定位，这表明这些蛋白质结合位点与HS5的形成有关。凝胶阻滞试验表明，在小鼠HS5A和HS5B中鉴定出的Ap1/NF-E2基序与NF-E2或类似蛋白质相互作用。对原代小鼠细胞的研究表明，HS5在所有测试的造血组织（胎肝、成年胸腺和脾脏）中形成，这表明该HS不是红系谱系特异性的。在小鼠脑中检测到了HS5，但在小鼠肾脏或成年肝脏中未检测到，这表明该位点并非普遍存在。GATA-1和NF-E2基序（LCR的DNase I超敏位点的共同特征）的存在表明，HS5的组织方式与其他HSs类似。综上所述，我们的结果表明HS5是β-珠蛋白基因座控制区的固有组成部分。
