Sm B′ Activators

Chemical activators of Sm B′ can influence the protein's function by modulating the phosphorylation status of various components within the spliceosome, where Sm B′ operates. Phorbol 12-myristate 13-acetate (PMA), for instance, activates Protein Kinase C (PKC), which can phosphorylate proteins that are crucial for mRNA processing, thus activating Sm B′. Similarly, Forskolin can elevate intracellular cAMP levels, thereby activating Protein Kinase A (PKA) which also targets proteins associated with mRNA splicing, thereby enhancing Sm B′ activity. Another compound, Ionomycin, increases intracellular calcium concentrations, which in turn activates calcium-dependent kinases capable of phosphorylating spliceosomal components, supporting Sm B′ activation. Epidermal Growth Factor (EGF) engages the MAPK/ERK pathway, leading to the phosphorylation of splicing-related proteins and the subsequent activation of Sm B′.

Additionally, Okadaic Acid and Calyculin A are known to inhibit protein phosphatases 1 and 2A, leading to a net increase in phosphorylation levels of splicing factors, which can support the active state of Sm B′. Anisomycin, by activating stress-activated protein kinases, can phosphorylate splicing factors, which in turn can activate Sm B′. Dibutyryl-cAMP (db-cAMP), a cAMP analog, activates PKA, which might result in phosphorylation and activation of Sm B′. Similarly, A23187, acting as a calcium ionophore, can enhance the phosphorylation state of Sm B′ by increasing intracellular calcium levels. Sodium Orthovanadate, a protein tyrosine phosphatase inhibitor, can also contribute to the activation of Sm B′ by maintaining a high phosphorylation level of proteins involved in splicing. Lastly, Bisindolylmaleimide I, though primarily an inhibitor of PKC, can indirectly activate other kinases through feedback mechanisms, which then might lead to the phosphorylation and activation of Sm B′, highlighting the intricate regulatory networks that control spliceosomal activity.