Abstract
Ethylene signaling pathway leads to rapid gene activation by two hierarchies of transcription factors with EIN3/EIL proteins as primary ones and ERF proteins as secondary ones. The role of chromatin modifications during the rapid gene activation is not known. In this work we studied trimethylated histone H3 lysine 4 (H3K4me3) and lysine 27 (H3K27me3), two opposite histone methylation marks for gene activity, during the induction course of three ethylene-responsive genes (ERF1, AtERF14 and ChiB). We found that the three genes displayed different histone modification profiles before induction. After induction, H3K4me3 was increased in the 5′ region and the gene body of ERF1, while H3K27me3 was decreased in the promoter of AtERF14. But the modification changes were later than the gene activation. Analysis of other rapidly inducible ERF genes confirmed the observation. In addition, histone H2A.Z occupancy on the three genes and the association of the H3K27me3-binding protein LHP1 with AtERF14 and ChiB were not affected by the inductive signal. However, the mutation of genes encoding H2A.Z and LHP1 attenuated and enhanced respectively the induction of target genes and altered H3K4me3. These results indicate that the induction of ethylene-responsive genes does not require immediate modulation of H3K4me3 and H3K27me3 and dissociation of LHP1 and H2A.Z from the targets, and suggest that the chromatin structure of the genes before induction is committed for transcriptional activation and that H3K4me3 is not required for ethylene-responsive gene activation, but may serve as a mark for gene activity.
Highlights
In addition to transcription factors chromatin structure plays an important role in the regulation of gene expression
H3K4me3 was not detected over AtERF14 (Fig. 1B)
Analysis of five additional ERF genes (ORA59, TDR1, AtERF1, AtERF2 and AtERF11) revealed that TDR1 displayed a high level of H3K27me3 but a low level of H3K4me3, while the other four genes showed a high level of H3K4me3 but a low level of H3K27me3 (Fig. S2)
Summary
In addition to transcription factors chromatin structure plays an important role in the regulation of gene expression. Chromatin structure change includes histone modifications and DNA methylation, histone variant deposition and chromatin remodeling. Especially H3K4 trimethylation and H3K27 trimethylation, have been largely reported to be tightly associated with gene transcription activity [1,2]. H3K4me is associated with highly expressed and/or housekeeping genes whereas H3K27me marks under-expressed and/or repressed tissue-specific genes [1,2]. Both modification marks could be recognized by different chromatin factors through specific protein domains. Histone variant H2A.Z is another important regulator of gene expression which is deposited into nucleosome by SWR complex. Recent analysis in various species has revealed that activation of H2A.Z-regulated genes was accompanied by eviction of H2A.Z or replacement of
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