dELTA-MS: A Mass Spectrometry-Based Proteomics Approach for Identifying ADP-Ribosylation Sites and Forms.

ADP-ribosylation, characterized by the addition of adenosine diphosphate ribose, can occur in both monomeric (MARylation) and polymeric (PARylation) forms. Little is known about the specific contributions of MARylation and PARylation to cellular processes due to a lack of tools for jointly investigating these individual forms. We present a novel mass spectrometry (MS)-based proteomics approach that preserves information about the native ADP-ribosylation form associated with the modification site within a single proteomics experiment.

PERIOD phosphorylation leads to feedback inhibition of CK1 activity to control circadian period.

PERIOD (PER) and Casein Kinase 1δ regulate circadian rhythms through a phosphoswitch that controls PER stability and repressive activity in the molecular clock. CK1δ phosphorylation of the familial advanced sleep phase (FASP) serine cluster embedded within the Casein Kinase 1 binding domain (CK1BD) of mammalian PER1/2 inhibits its activity on phosphodegrons to stabilize PER and extend circadian period. Here, we show that the phosphorylated FASP region (pFASP) of PER2 directly interacts with and inhibits CK1δ.

Casein kinase 1 dynamics underlie substrate selectivity and the PER2 circadian phosphoswitch.

Post-translational control of PERIOD stability by Casein Kinase 1δ and ε (CK1) plays a key regulatory role in metazoan circadian rhythms. Despite the deep evolutionary conservation of CK1 in eukaryotes, little is known about its regulation and the factors that influence substrate selectivity on functionally antagonistic sites in PERIOD that directly control circadian period. Here we describe a molecular switch involving a highly conserved anion binding site in CK1.

CK1δ/ε protein kinase primes the PER2 circadian phosphoswitch.

Multisite phosphorylation of the PERIOD 2 (PER2) protein is the key step that determines the period of the mammalian circadian clock. Previous studies concluded that an unidentified kinase is required to prime PER2 for subsequent phosphorylation by casein kinase 1 (CK1), an essential clock component that is conserved from algae to humans. These subsequent phosphorylations stabilize PER2, delay its degradation, and lengthen the period of the circadian clock.

Role of the vacuolar-ATPase in Sindbis virus infection.

Bafilomycin A(1) is a specific inhibitor of the vacuolar-ATPase (V-ATPase), which is responsible for pH homeostasis of the cell and for the acidification of endosomes. Bafilomycin A(1) has been commonly used as a method of inhibition of infection by viruses known or suspected to follow the path of receptor-mediated endocytosis and low-pH-mediated membrane fusion. The exact method of entry for Sindbis virus, the prototype alphavirus, remains undetermined.