Sumoylation of histone deacetylase 1 regulates MyoD signaling during myogenesis

Sumoylation, the conjugation of a small ubiquitin-like modifier (SUMO) protein to a target, has diverse cellular effects. However, the functional roles of the SUMO modification during myogenesis have not been fully elucidated. Here, we report that basal sumoylation of histone deacetylase 1 (HDAC1) enhances the deacetylation of MyoD in undifferentiated myoblasts, whereas further sumoylation of HDAC1 contributes to switching its binding partners from MyoD to Rb to induce myocyte differentiation. Differentiation in C2C12 skeletal myoblasts induced new immunoblot bands above HDAC1 that were gradually enhanced during differentiation. Using SUMO inhibitors and sumoylation assays, we showed that the upper band was caused by sumoylation of HDAC1 during differentiation. Basal deacetylase activity was not altered in the SUMO modification-resistant mutant HDAC1 K444/476R (HDAC1 2R). Either differentiation or transfection of SUMO1 increased HDAC1 activity that was attenuated in HDAC1 2R. Furthermore, HDAC1 2R failed to deacetylate MyoD. Binding of HDAC1 to MyoD was attenuated by K444/476R. Binding of HDAC1 to MyoD was gradually reduced after 2 days of differentiation. Transfection of SUMO1 induced dissociation of HDAC1 from MyoD but potentiated its binding to Rb. SUMO1 transfection further attenuated HDAC1-induced inhibition of muscle creatine kinase luciferase activity that was reversed in HDAC1 2R. HDAC1 2R failed to inhibit myogenesis and muscle gene expression. In conclusion, HDAC1 sumoylation plays a dual role in MyoD signaling: enhancement of HDAC1 deacetylation of MyoD in the basally sumoylated state of undifferentiated myoblasts and dissociation of HDAC1 from MyoD during myogenesis.

Uncleaved Dystrophin Induce Cardiac Myocyte Apoptosis in Coxsackievirus Infected Balb/C Background Mice Heart

It has been previously demonstrated that dystrophin is cleaved in the cardiac myocyte by the viral protease 2A following infection with Coxsackievirus B3 (CVB3). The viral protease 2A mediated cardiomyopathy can be prevented by inhibiting cleavage of dystrophin. However, it is less clear whether uncleaved dysdrophin have other heart protective effect in coxsackievirus infection. To address this, we generated a Balb/C background mouse that had a point mutation in dystrophin that prevents cleavage by protease 2A (KI). We show here that when mice expressing cleavage-resistant dystrophin were infected with CVB3, there was increased cardiac myocyte apoptosis. Bax and Bcl-X(L) mRNA ratio was significantly increased in KI mice heart compare to wild type mice heart. We found cleavage-resistant dystrophin induced the apoptosis related enzyme capspase-3 and caspase-8 activity. In addition, TUNEL stain was observed many TUNEL positive cardiac myocyte in KI mice heart compare to wild type mice heart (3.7% vs 0.3%). However, zVAD treatment for apoptosis blocking was significantly decreased myocardium damage and fibrosis in KI mice heart. These findings indicated that uncleaved dystrophin may have a critical role in cardiac myocyte viral propagation. Uncleaved dystrophin mutant induced cardiac myocyte apoptosis. It delayed coxsackievirus propagation in cardiac myocyte and could prevent cardiac myocyte death.

Bioinformatics Interpretation of Exome Sequencing: Blood Cancer

We had analyzed 10 exome sequencing data and single nucleotide polymorphism chips for blood cancer provided by the PGM21 (The National Project for Personalized Genomic Medicine) Award program. We had removed sample G06 because the pair is not correct and G10 because of possible contamination. In-house software somatic copy-number and heterozygosity alteration estimation (SCHALE) was used to detect one loss of heterozygosity region in G05. We had discovered 27 functionally important mutations. Network and pathway analyses gave us clues that NPM1, GATA2, and CEBPA were major driver genes. By comparing with previous somatic mutation profiles, we had concluded that the provided data originated from acute myeloid leukemia. Protein structure modeling showed that somatic mutations in IDH2, RASGEF1B, and MSH4 can affect protein structures.

ERRATUM: Acknowledgments Correction. Bioinformatics Interpretation of Exome Sequencing: Blood Cancer

The funding acknowledgment in this article was partially omitted as published.