Vigilin protein Vgl1 is required for heterochromatin-mediated gene silencing in Schizosaccharomyces pombe.

Heterochromatin is a conserved feature of eukaryotic genomes and regulates various cellular processes, including gene silencing, chromosome segregation, and maintenance of genome stability. In the fission yeast Schizosaccharomyces pombe, heterochromatin formation involves methylation of lysine 9 in histone H3 (H3K9), which recruits Swi6/HP1 proteins to heterochromatic loci. The Swi6/HP1-H3K9me3 chromatin complex lies at the center of heterochromatic macromolecular assemblies and mediates many functions of heterochromatin by recruiting a diverse set of regulators. However, additional factors may be required for proper heterochromatin organization, but they are not fully known. Here, using several molecular and biochemical approaches, we report that Vgl1, a member of a large family of multiple KH-domain proteins, collectively known as vigilins, is indispensable for the heterochromatin-mediated gene silencing in S. pombe ChIP analysis revealed that Vgl1 binds to pericentromeric heterochromatin in an RNA-dependent manner and that Vgl1 deletion leads to loss of H3K9 methylation and Swi6 recruitment to centromeric and telomeric heterochromatic loci. Furthermore, we show that Vgl1 interacts with the H3K9 methyltransferase, Clr4, and that loss of Vgl1 impairs Clr4 recruitment to heterochromatic regions of the genome. These findings uncover a novel role for Vgl1 as a key regulator in heterochromatin-mediated gene silencing in S. pombe.

Farooq Z ，Abdullah E ，Banday S ，Ganai SA ，Rashid R ，Mushtaq A ，Rashid S ，Altaf M ... -  《-》

Role of Swi6/HP1 self-association-mediated recruitment of Clr4/Suv39 in establishment and maintenance of heterochromatin in fission yeast.

Haldar S ，Saini A ，Nanda JS ，Saini S ，Singh J ... -  《-》

Interaction of APC/C-E3 ligase with Swi6/HP1 and Clr4/Suv39 in heterochromatin assembly in fission yeast.

Dubey RN ，Nakwal N ，Bisht KK ，Saini A ，Haldar S ，Singh J ... -  《-》

Ubiquitin ligase component Cul4 associates with Clr4 histone methyltransferase to assemble heterochromatin.

Jia S ，Kobayashi R ，Grewal SI 《NATURE CELL BIOLOGY》

Coordination of DNA replication and histone modification by the Rik1-Dos2 complex.

Histone modification marks have an important role in many chromatin processes. During DNA replication, both heterochromatin and euchromatin are disrupted ahead of the replication fork and are then reassembled into their original epigenetic states behind the fork. How histone marks are accurately inherited from generation to generation is still poorly understood. In fission yeast (Schizosaccharomyces pombe), RNA interference (RNAi)-mediated histone methylation is cell cycle regulated. Centromeric repeats are transiently transcribed in the S phase of the cell cycle and are processed into short interfering RNAs (siRNAs) by the complexes RITS (RNA-induced initiation of transcriptional gene silencing) and RDRC (RNA-directed RNA polymerase complex). The small RNAs together with silencing factors-including Dos1 (also known as Clr8 and Raf1), Dos2 (also known as Clr7 and Raf2), Rik1 and Lid2-promote heterochromatic methylation of histone H3 at lysine 9 (H3K9) by a histone methyltransferase, Clr4 (refs 8-13). The methylation of H3K9 provides a binding site for Swi6, a structural and functional homologue of metazoan heterochromatin protein 1 (HP1). Here we characterize a silencing complex in fission yeast that contains Dos2, Rik1, Mms19 and Cdc20 (the catalytic subunit of DNA polymerase-ε). This complex regulates RNA polymerase II (RNA Pol II) activity in heterochromatin and is required for DNA replication and heterochromatin assembly. Our findings provide a molecular link between DNA replication and histone methylation, shedding light on how epigenetic marks are transmitted during each cell cycle.

Li F ，Martienssen R ，Cande WZ 《-》