Doan Loretta L, Porter Susan D, Duan Zhijun, Flubacher Marcella M, Montoya Diego, Tsichlis Philip N, Horwitz Marshall, Gilks C Blake, Grimes H Leighton
Institute for Cellular Therapeutics, University of Louisville, KY, USA.
Nucleic Acids Res. 2004 May 6;32(8):2508-19. doi: 10.1093/nar/gkh570. Print 2004.
Growth factor independence-1 (GFI1) and GFI1B are closely related, yet differentially expressed transcriptional repressors with nearly identical DNA binding domains. GFI1 is upregulated in the earliest thymocyte precursors, while GFI1B expression is restricted to T lymphopoiesis stages coincident with activation. Transgenic expression of GFI1 potentiates T-cell activation, while forced GFI1B expression decreases activation. Both mice and humans with mutant Gfi1 display lymphoid abnormalities. Here we describe autoregulation of Gfi1 in primary mouse thymocytes and a human T-cell line. GFI1 binding to cis-element sequences conserved between rat, mouse and human Gfi1 mediates direct and potent transcriptional repression. In addition, dramatic regulation of Gfi1 can also be mediated by GFI1B. These data provide the first example of a gene directly targeted by GFI1 and GFI1B. Moreover, they support a role for auto- and trans-regulation of Gfi1 by GFI1 and GFI1B in maintaining the normal expression patterns of Gfi1, and suggest that GFI1B may indirectly affect T-cell activation through repression of Gfi1.
生长因子独立性-1(GFI1)和GFI1B密切相关,但却是差异表达的转录抑制因子,它们具有几乎相同的DNA结合结构域。GFI1在最早的胸腺细胞前体中上调,而GFI1B的表达则局限于与激活同时发生的T淋巴细胞生成阶段。GFI1的转基因表达增强T细胞激活,而强制表达GFI1B则降低激活。Gfi1突变的小鼠和人类均表现出淋巴样异常。在此,我们描述了原代小鼠胸腺细胞和人T细胞系中Gfi1的自动调节。GFI1与大鼠、小鼠和人类Gfi1之间保守的顺式元件序列结合,介导直接且有效的转录抑制。此外,Gfi1的显著调节也可由GFI1B介导。这些数据提供了GFI1和GFI1B直接靶向的基因的首个实例。此外,它们支持GFI1和GFI1B对Gfi1进行自动调节和反式调节在维持Gfi1正常表达模式中的作用,并表明GFI1B可能通过抑制Gfi1间接影响T细胞激活。