The role of factors regulating transcript elongation by RNA polymerase II in tuning plant gene expression programs

点击翻译按钮获取中文摘要

The genomic DNA of eukaryotic organisms is packaged into a nucleoprotein structure termed chromatin, and nucleosome particles represent the basic unit of chromatin. Hence, by restricting the accessibility of DNA nucleosomes repress various DNA-dependent processes such as gene transcription. Accordingly, RNA polymerase II (RNAPII), the enzyme that transcribes protein-coding genes (synthesising mRNAs), requires different assistant factors, which facilitate productive transcript elongation of DNA templates assembled into nucleosomes. Among the proteins that promote the elongation phase of RNAPII transcription are the so-called transcript elongation factors (TEFs). They represent a heterogeneous group of proteins with diverse functions including modulating the catalytic properties of RNAPII or destabilising nucleosomes in the path of the enzyme, allowing efficient mRNA synthesis. In line with their function in gene transcription TEFs contribute to adjusting accurately cellular transcript levels.We have previously characterised various TEFs of the Arabidopsis plant model demonstrating that mutant plants deficient in certain TEFs display distinct defects in growth and development. Not much is known about functional interactions between TEFs that associate with elongating RNAPII forming the transcript elongation complex. We will analyse double-mutant plants lacking different pairs of TEFs to examine their cooperation on the molecular level (recruitment, functional interdependence). Interestingly, only the expression of specific subsets of genes is impaired by the elongation defects brought about by the absence of certain TEFs. Employing genome-wide analyses (transcriptomics, chromatin immunoprecipitation) we intend to identify features of target genes that determine the requirement for TEF action to achieve efficient transcription. Establishing a transcript elongation reporter construct will yield further clues about the mechanism of action of TEFs in planta. In conclusion, the proposed project will provide novel insight into TEF action during RNAPII transcription in vivo and their role in establishing precise gene expression profiles required for proper plant development.