Discovery and Functional Characterization of a Potent, Selective, and Metabolically Stable PROTAC of the Protein Kinases DYRK1A and DYRK1B.

Small-molecule-induced protein degradation has emerged as a promising pharmacological modality for inactivating disease-relevant protein kinases. DYRK1A and DYRK1B are closely related protein kinases that are involved in pathological processes such as neurodegeneration, cancer development, and adaptive immune homeostasis. Herein, we report the development of the first DYRK1 proteolysis targeting chimeras (PROTACs) that combine a new ATP-competitive DYRK1 inhibitor with ligands for the E3 ubiquitin ligase component cereblon (CRBN) to induce ubiquitination and subsequent proteasomal degradation of DYRK1A and DYRK1B.

Type III Mirizzi, successfully treated with a free gallbladder flap, a case report.

Background: Mirizzi syndrome is a type of biliary obstruction caused by an impacted stone in the gallbladder neck or cystic duct that causes and extrinsic obstruction of the common bile duct, this condition if left untreated can lead to duct erosion, fistula, and cholangitis. Preoperative diagnosis is difficult since if not diagnosed correctly can elevate the risk of intraoperative bile duct injury.

Case Presentation: We present the case of a 61-year-old patient, she presented to our hospital with obstructive jaundice, and a type III Mirizzi syndrome was identified.

The Need for Speed: Run-On Oligomer Filament Formation Provides Maximum Speed with Maximum Sequestration of Activity.

Here, we investigate an unusual antiviral mechanism developed in the bacterium SgrAI is a type II restriction endonuclease that forms run-on oligomer filaments when activated and possesses both accelerated DNA cleavage activity and expanded DNA sequence specificity. Mutations disrupting the run-on oligomer filament eliminate the robust antiphage activity of wild-type SgrAI, and the observation that even relatively modest disruptions completely abolish this anti-viral activity shows that the greater speed imparted by the run-on oligomer filament mechanism is critical to its biological function. Simulations of DNA cleavage by SgrAI uncover the origins of the kinetic advantage of this newly described mechanism of enzyme regulation over more conventional mechanisms, as well as the origin of the sequestering effect responsible for the protection of the host genome against damaging DNA cleavage activity of activated SgrAI.

The run-on oligomer filament enzyme mechanism of SgrAI: Part 1. Assembly kinetics of the run-on oligomer filament.

Filament or run-on oligomer formation by metabolic enzymes is now recognized as a widespread phenomenon having potentially unique enzyme regulatory properties and biological roles, and its dysfunction is implicated in human diseases such as cancer, diabetes, and developmental disorders. SgrAI is a bacterial allosteric type II restriction endonuclease that binds to invading phage DNA, may protect the host DNA from off-target cleavage activity, and forms run-on oligomeric filaments with enhanced DNA-cleavage activity and altered DNA sequence specificity. However, the mechanisms of SgrAI filament growth, cooperativity in filament formation, sequestration of enzyme activity, and advantages over other filament mechanisms remain unknown.

The run-on oligomer filament enzyme mechanism of SgrAI: Part 2. Kinetic modeling of the full DNA cleavage pathway.

Filament or run-on oligomer formation by enzymes is now recognized as a widespread phenomenon with potentially unique enzyme regulatory properties and biological roles. SgrAI is an allosteric type II restriction endonuclease that forms run-on oligomeric filaments with activated DNA cleavage activity and altered DNA sequence specificity. In this two-part work, we measure individual steps in the run-on oligomer filament mechanism to address specific questions of cooperativity, trapping, filament growth mechanisms, and sequestration of activity using fluorophore-labeled DNA, kinetic FRET measurements, and reaction modeling with global data fitting.