Inhibition of IRF5 cellular activity with cell-penetrating peptides that target homodimerization.

The transcription factor interferon regulatory factor 5 (IRF5) plays essential roles in pathogen-induced immunity downstream of Toll-, nucleotide-binding oligomerization domain-, and retinoic acid-inducible gene I-like receptors and is an autoimmune susceptibility gene. Normally, inactive in the cytoplasm, upon stimulation, IRF5 undergoes posttranslational modification(s), homodimerization, and nuclear translocation, where dimers mediate proinflammatory gene transcription. Here, we report the rational design of cell-penetrating peptides (CPPs) that disrupt IRF5 homodimerization. Biochemical and imaging analysis shows that IRF5-CPPs are cell permeable, noncytotoxic, and directly bind to endogenous IRF5. IRF5-CPPs were selective and afforded cell type- and species-specific inhibition. In plasmacytoid dendritic cells, inhibition of IRF5-mediated interferon-α production corresponded to a dose-dependent reduction in nuclear phosphorylated IRF5 [p(Ser462)IRF5], with no effect on pIRF5 levels. These data support that IRF5-CPPs function downstream of phosphorylation. Together, data support the utility of IRF5-CPPs as novel tools to probe IRF5 activation and function in disease.

Fragment-Based Drug Design of Novel Pyranopyridones as Cell Active and Orally Bioavailable Tankyrase Inhibitors.

Tankyrase activity has been linked to the regulation of intracellular axin levels, which have been shown to be crucial for the Wnt pathway. Deregulated Wnt signaling is important for the genesis of many diseases including cancer. We describe herein the discovery and development of a new series of tankyrase inhibitors. These pyranopyridones are highly active in various cell-based assays. A fragment/structure based optimization strategy led to a compound with good pharmacokinetic properties that is suitable for in vivo studies and further development.

Structural basis for lower lysine methylation state-specific readout by MBT repeats of L3MBTL1 and an engineered PHD finger.

Human L3MBTL1, which contains three malignant brain tumor (MBT) repeats, binds monomethylated and dimethylated lysines, but not trimethylated lysines, in several histone sequence contexts. In crystal structures of L3MBTL1 complexes, the monomethyl- and dimethyllysines insert into a narrow and deep cavity of aromatic residue-lined pocket 2, while a proline ring inserts into shallower pocket 1. We have also engineered a single Y to E substitution within the aromatic cage of the BPTF PHD finger, resulting in a reversal of binding preference from trimethyl- to dimethyllysine in an H3K4 sequence context. In both the "cavity insertion" (L3MBTL1) and "surface groove" (PHD finger) modes of methyllysine recognition, a carboxylate group both hydrogen bonds and ion pairs to the methylammonium proton. Our structural and binding studies of these two modules provide insights into the molecular principles governing the decoding of lysine methylation states, thereby highlighting a methylation state-specific layer of histone mark readout impacting on epigenetic regulation.