Transcriptional regulation is modulated in part by chromatin-remodeling enzymes that control gene accessibility by altering chromatin compaction or nucleosome positioning. Brahma-related gene 1 (Brg1), a catalytic subunit of the mammalian SWI/SNF chromatin-remodeling enzymes, is required for both myoblast proliferation and differentiation, and the control of Brg1 phosphorylation by calcineurin, PKCbeta1, and p38 regulates the transition to differentiation. However, we hypothesized that Brg1 activity might be regulated by additional kinases. Here, we report that Brg1 is also a target of casein kinase 2 (CK2), a serine/threonine kinase, in proliferating myoblasts. We found that CK2 interacts with Brg1, and mutation of putative phosphorylation sites to non-phosphorylatable (Ser to Ala, SA) or phosphomimetic residues (Ser to Glu, SE) reduced Brg1 phosphorylation by CK2. Although BRG1-deleted myoblasts that ectopically express the SA-Brg1 mutant proliferated similarly to the parental cells or cells ectopically expressing wild-type (WT) Brg1, ectopic expression of the SE-Brg1 mutant reduced proliferation and increased cell death, similar to observations from cells lacking Brg1. Moreover, pharmacological inhibition of CK2 increased myoblast proliferation. Furthermore, the Pax7 promoter, which controls expression of a key transcription factor required for myoblast proliferation, was in an inaccessible chromatin state in the SE-Brg1 mutant, suggesting that hyperphosphorylated Brg1 cannot remodel chromatin. WT-, SA-, and SE-Brg1 exhibited distinct differences in interacting with and affecting expression of the SWI/SNF subunits Baf155 and Baf170 and displayed differential sub-nuclear localization. Our results indicate that CK2-mediated phosphorylation of Brg1 regulates myoblast proliferation and provides insight into one mechanism by which composition of the mammalian SWI/SNF enzyme complex is regulated.

Epithelial-mesenchymal transition (EMT) is a reversible cellular process, characterized by changes in gene expression and activation of proteins, favoring the trans-differentiation of the epithelial phenotype to a mesenchymal phenotype. This process increases cell migration and invasion of tumor cells, progression of the cell cycle, and resistance to apoptosis and chemotherapy, all of which support tumor progression. One of the signaling pathways involved in tumor progression is the MAPK pathway. Within this family, the ERK subfamily of proteins is known for its contributions to EMT. The ERK subfamily is divided into typical (ERK 1/2/5), and atypical (ERK 3/4/7/8) members. These kinases are overexpressed and hyperactive in various types of cancer. They regulate diverse cellular processes such as proliferation, migration, metastasis, resistance to chemotherapy, and EMT. In this context, in vitro and in vivo assays, as well as studies in human patients, have shown that ERK favors the expression, function, and subcellular relocalization of various proteins that regulate EMT, thus promoting tumor progression. In this review, we discuss the mechanistic roles of the ERK subfamily members in EMT and tumor progression in diverse biological systems.

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease is the most common form of motor neuron disease. In familial ALS, Multiple mutations of, PFN1 gene a well-known actin-binding protein have been linked to ALS disease recently. Phosphorylation in many degenerative conditions plays an important role in disease mechanism but its potential role in ALS remains not fully understood. We sought to look further into not previously studied phosphorylation of PFN1 as a potential contributor to aggregation and toxicity in ALS. Using different histochemistry and cytochemistry and molecular biology approaches, we observed that phosphorylation on Profilin shows a very distinctive pattern in PFN1C71G andSOD1G93A disease models. This modification is abundantly found in both astrocytes and white matter which latter indeed marks a staining pattern that is indistinguishable between two ALS mice model compared to controls. Interestingly, pPFN1 reactive areas colocalized with Myelin in the spinal cord are frequently found in the proximity of CD68 positive macrophages. Moreover, biochemical fractionation using ultracentrifugation detects endogenous pPFN1 in the highly insoluble fraction of protein lysate from both PFN1C71G andSOD1G93A model. Finally, a similar staining pattern to the ALS mice model was also observed in human sporadic ALS cases. Overall, our results suggest for the first time a role for phosphorylation of PFN1 in protein aggregation and white matter pathology in ALS that will shed more light on the mechanism of disease and developing potential therapeutics in near future.

The mycobacterial cell wall is a dynamic structure that protects Mycobacterium tuberculosis and its relatives from environmental stresses. Modulation of cell wall metabolism under stress is thought to be responsible for decreased cell wall permeability and increased tolerance to antibiotics. The signaling pathways that control cell wall metabolism under stress, however, are poorly understood. Here, we examine the signaling capacity of a cell wall master regulator, the Serine Threonine Phosphatase PstP, in the model organism Mycobacterium smegmatis. We studied how interference with a regulatory phosphorylation site on PstP affects growth, cell wall metabolism and antibiotic tolerance. We find that a phospho-mimetic mutation, pstP T171E, slows growth, misregulates both mycolic acid and peptidoglycan metabolism in different conditions, and interferes with antibiotic tolerance. These data suggest that phosphorylation on PstP controls its substrate specificity and is important in the transition between growth and stasis.