Hematology Department, Hospital Clinico San Carlos, University Complutense, Madrid, Spain.
Ann Hematol. 2010 Aug;89(8):759-65. doi: 10.1007/s00277-009-0900-x. Epub 2010 Feb 9.
Growth factor-independence 1b (Gfi1b) is a zinc finger transcription factor essential for erythroid and megakaryocytic development. To better understand Gfi1b regulation and to know the implication of the level of expression of this gene in human pathology, we have searched for promoter punctual sequence variations in 214 patients with different hematological diseases. We found two previously unknown congenital mutations at evolutionary conserved GATA and octamer-binding (Oct) transcription factor sites. The Oct site mutation was also found in five relatives of the patient. The GATA motif mutation reduced promoter activity by 50% in vitro, while homozygous patients with the octamer site mutation showed a four-to-five times increase of Gfi1b RNA in platelets. Electrophoretic mobility shift analyses demonstrated that different protein complexes bind to both sites and that binding is reduced by the mutations. Finally, we found that GATA-1 and Oct-1 are the main components of each complex. This study provides evidences of a new mechanism for Gfi1b repression. This is also the first report of Gfi1b mutations with a functional implication; further investigation and follow-up will clarify the involvement of these mutations in hematological disease.
生长因子独立性 1b（Gfi1b）是一种锌指转录因子，对红细胞和巨核细胞的发育至关重要。为了更好地了解 Gfi1b 的调控机制，并了解该基因在人类病理学中的表达水平的意义，我们在 214 名患有不同血液疾病的患者中搜索了启动子的点突变序列。我们在进化上保守的 GATA 和八聚体结合（Oct）转录因子位点发现了两个以前未知的先天性突变。该 Oct 位点突变也在患者的五位亲属中被发现。体外实验表明，GATA 基序突变使启动子活性降低了 50%，而杂合子患者的血小板中 Gfi1b RNA 增加了四到五倍。电泳迁移率变动分析表明，不同的蛋白质复合物结合到两个位点，而突变则降低了结合。最后，我们发现 GATA-1 和 Oct-1 是每个复合物的主要组成部分。这项研究为 Gfi1b 抑制的新机制提供了证据。这也是首次报道具有功能意义的 Gfi1b 突变；进一步的研究和随访将阐明这些突变在血液疾病中的参与。
