Project description:The functional determinants of histone H3 Lys-4 trimethylation (H3K4me3), their potential dependency on histone H2B monoubiquitination (H2Bub) and their contribution in defining gene expression programs are poorly defined in plant systems. Differently from S. cerevisiae in which a single SET1 protein catalyzes H3 Lys-4 trimethylation as part of COMPASS (COMPlex of proteins ASsociated with SET1), this activity involves multiple histone methyltransferases (HMTs) in Arabidopsis thaliana, among which the plant-specific SDG2 (SET DOMAIN GROUP2) has a prominent role. Here we report that SDG2 co-regulates hundreds genes with SWD2-like b (S2Lb), a plant ortholog of the Swd2 axillary subunit of the evolutionarily conserved COMPASS complex. Accordingly, S2Lb associates with the AtCOMPASS core subunit WDR5a within a high-molecular weight complex and is required for proper H3K4me3 enrichment over genes highly occupied by RNA Polymerase II. S2Lb knock-out plants display little transcriptomic defects, suggesting that H3K4me3 deposition is important for optimal gene induction rather than for determining on/off transcriptional states. We further report that S2Lb and H3K4me3 are accurately targeted over most genes in hub1 mutant plants lacking histone H2B monoubiquitination. Collectively, our study indicates that a plant-specific COMPASS-like complex acting mainly through an H2Bub-independent mechanism is a major determinant of H3K4me3 deposition in Arabidopsis.
Project description:The functional determinants of histone H3 Lys-4 trimethylation (H3K4me3), their potential dependency on histone H2B monoubiquitination (H2Bub) and their contribution in defining gene expression programs are poorly defined in plant systems. Differently from S. cerevisiae in which a single SET1 protein catalyzes H3 Lys-4 trimethylation as part of COMPASS (COMPlex of proteins ASsociated with SET1), this activity involves multiple histone methyltransferases (HMTs) in Arabidopsis thaliana, among which the plant-specific SDG2 (SET DOMAIN GROUP2) has a prominent role. Here we report that SDG2 co-regulates hundreds genes with SWD2-like b (S2Lb), a plant ortholog of the Swd2 axillary subunit of the evolutionarily conserved COMPASS complex. Accordingly, S2Lb associates with the AtCOMPASS core subunit WDR5a within a high-molecular weight complex and is required for proper H3K4me3 enrichment over genes highly occupied by RNA Polymerase II. S2Lb knock-out plants display little transcriptomic defects, suggesting that H3K4me3 deposition is important for optimal gene induction rather than for determining on/off transcriptional states. We further report that S2Lb and H3K4me3 are accurately targeted over most genes in hub1 mutant plants lacking histone H2B monoubiquitination. Collectively, our study indicates that a plant-specific COMPASS-like complex acting mainly through an H2Bub-independent mechanism is a major determinant of H3K4me3 deposition in Arabidopsis.
Project description:The functional determinants of histone H3 Lys-4 trimethylation (H3K4me3), their potential dependency on histone H2B monoubiquitination (H2Bub) and their contribution in defining gene expression programs are poorly defined in plant systems. Differently from S. cerevisiae in which a single SET1 protein catalyzes H3 Lys-4 trimethylation as part of COMPASS (COMPlex of proteins ASsociated with SET1), this activity involves multiple histone methyltransferases (HMTs) in Arabidopsis thaliana, among which the plant-specific SDG2 (SET DOMAIN GROUP2) has a prominent role. Here we report that SDG2 co-regulates hundreds genes with SWD2-like b (S2Lb), a plant ortholog of the Swd2 axillary subunit of the evolutionarily conserved COMPASS complex. Accordingly, S2Lb associates with the AtCOMPASS core subunit WDR5a within a high-molecular weight complex and is required for proper H3K4me3 enrichment over genes highly occupied by RNA Polymerase II. S2Lb knock-out plants display little transcriptomic defects, suggesting that H3K4me3 deposition is important for optimal gene induction rather than for determining on/off transcriptional states. We further report that S2Lb and H3K4me3 are accurately targeted over most genes in hub1 mutant plants lacking histone H2B monoubiquitination. Collectively, our study indicates that a plant-specific COMPASS-like complex acting mainly through an H2Bub-independent mechanism is a major determinant of H3K4me3 deposition in Arabidopsis.
Project description:The functional determinants of histone H3 Lys-4 trimethylation (H3K4me3), their potential dependency on histone H2B monoubiquitination (H2Bub) and their contribution in defining gene expression programs are poorly defined in plant systems. Differently from S. cerevisiae in which a single SET1 protein catalyzes H3 Lys-4 trimethylation as part of COMPASS (COMPlex of proteins ASsociated with SET1), this activity involves multiple histone methyltransferases (HMTs) in Arabidopsis thaliana, among which the plant-specific SDG2 (SET DOMAIN GROUP2) has a prominent role. Here we report that SDG2 co-regulates hundreds genes with SWD2-like b (S2Lb), a plant ortholog of the Swd2 axillary subunit of the evolutionarily conserved COMPASS complex. Accordingly, S2Lb associates with the AtCOMPASS core subunit WDR5a within a high-molecular weight complex and is required for proper H3K4me3 enrichment over genes highly occupied by RNA Polymerase II. S2Lb knock-out plants display little transcriptomic defects, suggesting that H3K4me3 deposition is important for optimal gene induction rather than for determining on/off transcriptional states. We further report that S2Lb and H3K4me3 are accurately targeted over most genes in hub1 mutant plants lacking histone H2B monoubiquitination. Collectively, our study indicates that a plant-specific COMPASS-like complex acting mainly through an H2Bub-independent mechanism is a major determinant of H3K4me3 deposition in Arabidopsis.
Project description:project abstract : H3K4 methylation is a well-conserved histone modification from yeast to human. Because H3K4 methylase Set1 and its complex, COMPASS (Complex of proteins associated with Set1), are conserved from yeast to humans, budding yeast has been studied as an acceptable model organism. Since COMPASS components affect Set1 protein stability and H3K4 methylation activity variously, it is important to study how Set1 is regulated by complex components. However, deletion mutant of Swd2 component of COMPASS is not viable, although overexpression of Sen1 fragment enables the construction of Swd2 deletion mutant. This study found that positioning epitope tag to the N-terminal of Swd2 did not decrease interaction between Swd2 and Set1, but reduced the stability of both proteins, Swd2 and Set1, and global H3K4 methylation. Also, we observed that overexpression of N-terminal tagged Swd2 caused increased Set1 protein level and bulk H3K4 methylation. Therefore, Set1 protein can maintain its protein level only when enough Swd2 exist to cover the protein amount of Set1. Also, by comparing RNA sequencing analysis of N-terminal tagged Swd2 and Swd2 deletion mutant with Sen1 fragment overexpression, we isolated genes regulated by Swd2. In conclusion, we suggest that the abundance of Swd2 is important to regulate the protein stability of Set1 and the regulation of gene expression.