Elongator is a histone acetyltransferase (HAT) complex associated with RNA polymerase II (RNAPII) to facilitate transcription elongation. It consists of subunits Elp1-6 with Elp3 conferring HAT activity. Elongator is conserved in yeast, plants and humans. In humans, mutations in Elp genes cause neuronal diseases. In plants, Elongator is a positive regulator of cell proliferation during leaf and root growth. Elongator mutants have altered auxin signaling and responses to abscisic acid. Elongator regulates expression of specific genes, such as the light-regulated auxin response regulator IAA3/SHY2 and the clock regulator LHY during RNAPII transcription elongation. In addition, Elongator mutant seedlings show an altered light response and resemble triple phytochrome mutants. The working hypothesis is that Elongator acts as interface between phytochrome signaling and gene expression during transcription elongation to regulate processes such as the shade avoidance response. Different light qualities (low and high red/far red ratios) and seedlings of Elongator mutant or recombinant lines will be used to explore light-related Elongator target genes, pathways and interactors. In a first objective, light-regulated genome-wide targets and pathways of Elongator will be determined using microarrays, chromatin immunoprecipitation (ChIP-on-chip or ChIP-Seq) and iTRAQ proteome analysis. In a second objective, interactors of Elongator involved in light signaling and their target-specificity will be identified using tandem affinity purification, transient split-luciferase in vivo assay and ChIP-PCR. Genetic interactions between Elongator and light signaling mutants will also be investigated. In the third objective, the mechanism of Elongator action will be studied using ChIP-qPCR to check whether Elongator target genes contain abundantly stalled RNAPII at their 5’ region. Novel insight into chromatin-related regulation of gene expression during light activation will be obtained.
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