Bcl6 and Prdm1 (Blimp1) are a pair of transcriptional factors that repressing each other in mammals. Prdm1 represses the expression of bcl6 by binding a cis-element of the bcl6 gene in mammals. The homologs of Bcl6 and Prdm1 have been identified in teleost fish. However, whether these two factors regulate each other in the same way in fish like that in mammals is not clear. In this study, the regulation of bcl6aa by Prdm1 was investigated in medaka. The mRNA of bcl6aa has three variants (bcl6aaX1-X3) at the 5′-end by alternative splicing detected by RT-PCR. The three variants can be detected in adult tissues and developing embryos of medaka. Prdm1a and prdm1b are expressed in the tissues and embryos where and when bcl6aa is expressed. The expression of prdm1a was high while the expression of bcl6aa was low, and vice versa, detected in the spleen after stimulation with LPS or polyI:C. In vitro reporter assay indicated that bcl6aa could be directly repressed by both Prdm1a and Prdm1b in a dosage-dependent manner. After mutation of the key base, G, of all predicted binding sites in the core promoter region of bcl6aa, the repression by Prdm1a and/or Prdm1b disappeared. The binding site of Prdm1 in the bcl6aa gene is GAAAA(T/G). These results indicate that both Prdm1a and Prdm1b directly repress the expression of bcl6aa by binding their binding sites where the 5′-G is critical in medaka fish.

Bcl6 和 Prdm1 (Blimp1) 是一对在哺乳动物中相互抑制的转录因子。PRDM1阻遏表达BCL6通过结合的顺式元件BCL6在哺乳动物基因。已在硬骨鱼中鉴定出 Bcl6 和 Prdm1 的同源物。然而，这两个因素在鱼类中是否像哺乳动物一样以相同的方式相互调节尚不清楚。在这项研究中，Prdm1对 bcl6aa的调控在青鳉进行了研究。通过 RT-PCR 检测到的选择性剪接，bcl6aa的 mRNA在 5' 端具有三个变体 ( bcl6aaX1-X3 )。这三种变异可以在青鳉的成体组织和发育中的胚胎中检测到。prdm1a和prdm1bbcl6aa在表达bcl6aa 的地方和时间在组织和胚胎中表达。的表达prdm1a是高，而表达bcl6aa低，并且反之亦然，在用LPS或聚肌胞刺激后脾检测：C。体外报告基因检测表明bcl6aa可以被 Prdm1a 和 Prdm1b 以剂量依赖性方式直接抑制。在bcl6aa核心启动子区域中所有预测结合位点的关键碱基 G 发生突变后，Prdm1a 和/或 Prdm1b 的抑制消失。bcl6aa基因中Prdm1的结合位点是GAAAA(T/G)。这些结果表明，Prdm1a和Prdm1b两者直接抑制的表达bcl6aa 通过结合它们的结合位点，其中 5'-G 在鳉鱼中至关重要。