No abstract

Protein phosphatase is important for cellular events, and a family of protein phosphatases, the so-called C-terminal domain (CTD) of RNA polymerase II (RNAPII) phosphatases, has recently attracted attention. The CTD is the largest subunit of RNAPII and consists of a tandem repeated heptapeptide (Y 1 S 2 P 3 T 4 S 5 P 6 S 7 ).1 Seven active CTD phosphatases in the human genome are known and share the same catalytic domain architecture and DXDX(T/V) active site motif.2 Small CTD phosphatase 1 (SCP1) dephosphorylates the fifth phosphorylated serine of Y 1 S 2 P 3 T 4 S 5 P 6 S 7 in the CTD 2 and has been renamed CTD small phosphatase 1 (CTDSP1). Small CTD phosphatase 2 (SCP2) and small CTD phosphatase 3 (SCP3) have a similar sequence, threedimensional structure, and biochemical function to SCP1.

Small C‐terminal domain phosphatase 1(SCP1)'s biological function is significant in many cellular activities. Still, a recent study on neuroglioma cells emphasized the requirement of negative regulation of SCP1 in cancer invasion suppression. Due to the structural conservation of C‐terminal domain (CTD) phosphatases, we aimed to determine the peripherally targeting inhibitors, which reciprocally bind to an eccentric site on SCP1 using a multidisciplinary approach. From biochemical screening, we have identified two potential inhibitors, which showed twofold to threefold selectivity toward SCP1 compared to Dullard. Dullard was utilized as a negative control as it is a small CTD phosphatase that contains structural similarities to SCP1. Besides, from in silico approaches like protein–ligand docking and molecular dynamics analyses, we have successfully discovered two allosteric inhibitors of napthoquinone family compounds explicitly binding to the unique hydrophobic pocket of SCP1 from 1000 molecular dockings and 125 ns of dynamics simulation studies, respectively.