Abstract
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.
Highlights
Bcl6 (B-Cell Lymphoma 6) is a member of the POK (POZ and Krüppel) ⁄ZBTB protein family (Lee and Maeda 2012)
Three variants of bcl6aa were identified in medaka
Medaka bcl6aa existed in the tissues or embryos which expressing prdm1a or prdm1b
Summary
Bcl (B-Cell Lymphoma 6) is a member of the POK (POZ and Krüppel) ⁄ZBTB (zing finger and BTB) protein family (Lee and Maeda 2012). Bcl and Prdm are two transcription factors functioning in diverse tissues such as the immune system and bone, etc. Bcl inhibits but Prdm promotes osteoclastogenesis in mice (Miyauchi et al 2010). Prdm is highly expressed in the Th2 (T helper 2) cells and is required for normal Th2 humoral responses in vivo by repression of Bcl and Tbx (T-box transcription factor 21) which are necessary for Th1 cells (Cimmino et al 2008). Prdm inhibits Tfh differentiation and B cell maturation (Johnston et al 2009). Bcl directly inhibits prdm expression or binds to Bach (BTB domain and CNC homolog 2) to repress prdm and represses plasmocytic differentiation (Ochiai et al 2008; Tunyaplin et al 2004). Prdm directly represses bcl by binding to the bcl gene in both CD4 T cells and B cells (Cimmino et al 2008)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
