Active repressors have an intrinsic repression motif which interacts with the general transcription factors (TFs) or with other chromatin components, eventually inhibiting the binding of transcriptional activators. Transcriptional repressors act either in an active or passive manner. Regulation of gene expression is an interesting phenomenon with the participation of multiple players, some of which act as repressors of downstream genes and regulate their spatio-temporal expression pattern. The study reports a straightforward assay to analyze repressor activity, along with the identification of a strong DLN repressor from rice. Comparatively, rice has more DLN repressor encoding genes than Arabidopsis, and DLNSPP motif from rice is 40% stronger than the known Arabidopsis SRDX motif. The DLN hexapeptide motif is essential for repression, and at least two “DLN” residues cause maximal repression.
Srdx repressor domain Activator#
We have designed a simple yeast-based experiment wherein a DLN motif can successfully cause strong repression of downstream reporter genes, when fused to a transcriptional activator of rice or yeast. Most of the DLN repressome proteins have a single DLN motif, with higher relative percentage in the C-terminal region. Apart from DLNxxP motif conservation, DLNxP and DLNxxxP motifs with variable numbers/positions of proline and those without any proline conservation have been identified. In rice ( Oryza sativa), we have identified a total of 266 DLN repressor proteins, with the former motif and its modifications thereof comprising 227 transcription factors and 39 transcriptional regulators. They contain either DLNxxP or LxLxL as the identifying hexapeptide motif. In plants, a well-established class of repressors are proteins with an ERF-associated amphiphilic repression/EAR domain. Transcriptional regulation includes both activation and repression of downstream genes.
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