Project description:Eukaryotic euchromatin is the less compact chromatin and modified by many histone modifications such as H3 Lysine 36 methylation (H3K36me). Here we report a new chromatin state, Transcription Resistive, which is differentiated from activation and silencing. Transcription resistive is stamped by H3K36me with almost undetectable transcription activity but open chromatin state, and occupies most documented plant essential genes. Mutating SDG8, previously known as the major H3K36 methyltransferase in Arabidopsis, surprisingly elevates 78.7% H3K36me3 marked resistive loci, which count for 39.4% of the coding genome. Genetically, SDG8 prevents H3K36me activity of SDG4 at short and intron-less genes to secure plant fertility, while SDG8 collaborates with other H3K36me methyltransferases on long and intron-rich genes. Together, our results reveal SDG8 is the primary sensor to suppress excessive H3K36me, and uncovered the resistive is the conserved H3K36me-stamped novel transcription state in plants, highlighting the regulatory diversities and biological significances of H3K36 methylation in eukaryotes.
Project description:RNA polymerase II (Pol II) play an essential role in gene expression. Here, we adapted plant Native Elongation Transcript sequencing and Global Run On sequencing to profile nascent RNA genome wide in Arabidopsis. We found Pol II tends to accumulate downstream of transcription start site and pausing at proximal promoter is an important regulatory step for Pol II transcription although loosely controlled. Furthermore, the Pol II with unphosphorylated carboxyl-terminal domain (CTD) mainly accumulates downstream the TSS, while the Ser5P CTD Pol II associates with spliceosome, and the Ser2P CTD Pol II presents a sharp peak 250 base pair downstream of polyadenylation site indicating a stringent control of termination for protein coding genes; whilst the termination of noncoding genes is not. Active expressed genes can be classified into three clusters according to the distribution patterns of different Pol II isoforms. In summary, we demonstrated the modified plant GRO-seq and pNET-seq are suitable to study RNA Pol II dynamics in planta. Although transcription is conserved among high eukaryotes, Pol II has its feature in Arabidopsis.
Project description:Programmed constitutive heterochromatin silencing is essential for eukaryotic genome regulation, yet the initial step of this process is ambiguous. A large proportion of R-loops (RNA:DNA hybrids) had been unexpectedly identified within Arabidopsis pericentromeric heterochromatin with unknown functions. Through a genome-wide R-loop profiling screen, we find DDM1 (Decrease in DNA Methylation 1) is the primary restrictor of pericentromeric R-loops via its RNA:DNA helicase activity. Low levels of pericentromeric R-loops resolved by DDM1 co-transcriptionally can prime constitutive heterochromatin silencing. Furthermore, we demonstrate that DDM1 physically excludes histone H2A variant H2A.Z, and promotes H2A.W deposition for faithful heterochromatin initiation soon after R-loop clearance. The dual functions of DDM1 in R-loop resolution and H2A.Z eviction are essential for sperm nuclei structure maintenance in mature pollen. Our work unravels the co-transcriptional R-loop resolution coupled with accurate H2A variants deposition is the primary step of constitutive heterochromatin silencing in Arabidopsis, which might be conserved across eukaryotes.
Project description:Recently, we described a new animal model of CNS primitive neuroectodermal tumors (CNS-PNET), which was generated by orthotopic transplantation of human Radial Glial (RG) cells into NOD-SCID mice’s brain sub- ventricular zone. In the current study we conducted comprehensive RNA-Seq analyses to gain some insights on the mechanisms underlying tumorigenesis in this mouse model of CNS-PNET. Here we show that the RNA-Seq profiles derived from these tumors cluster with those reported for patients’ PNETs.
Project description:miRNA expression analysis of mouse glioma and PNET. Glioma was developed from SVZ cells through conditional codeletion of Pten/p53 or Rb/p53; while PNET was developed by codeletion of Rb/p53.