Welcome to Gaia! :: View User's Journal | Gaia Journals

Figure optionsDownload full-size imageDownload as PowerPoint slide
To investigate how the repression activity of the AhRR fragment (342–701) functions in the TK promoter-driven reporter system, we used the HDAC inhibitor, TSA, which reversed the repression of reporter gene BI-D1870 by the AhRR fragment (342–701) in a dose-dependent manner (Fig. 1C). These results suggest that the repression activity of the AhRR C-terminus is due to an HDAC activity. Since the C-terminal sequence of AhRR is well conserved among multiple mammalian species (Supplementary Fig. S1), we next searched for transcriptional corepressor, which interact with the AhRR C-terminus.
Isolation of ANKRA2 as a factor interacting with AhRR and interaction of AhRR with ANKRA2 and HDAC4 or HDAC5
To isolate a corepressor of AhRR, we performed a Cytotrap yeast two-hybrid screen with the C-terminal fragment of AhRR (342–701) used as bait (Fig. 2A) and isolated several clones including Dhx8, EB1, EB3, p21, Prostaglandin E receptor, EGF-containing fibrin-like extracellular matrix protein1, and ANKRA2. We chose ANKRA2 for further work in this paper, because ANKRA2 is reported to interact with HDAC4 and HDAC5 [18]. Recently, its mammalian paralogue, RFXANK has also been reported to interact with HDAC4 and HDAC5 [18] and to repress MHC class II promoter activation through association with HDAC4 and HDAC5 [19]. Taken together, these results suggest a potential role of ANKRA2 as mediator in transcriptional repression. ANKRA2 is a protein of 312 amino acids with consecutive 3 ankyrin repeats and the cDNA encoded a C-terminal fragment, amino acid 117–312 (Fig. 2A).