Thursday, May 23, 2013

Applications Thursday: High throughput screen for ribonuclease H2 small molecule inhibitors

Structure of RNase H (PDB id: 1JL1) generated
using PyMol with preset: pretty
Ribonuclease H2 (RNase H2) is an enzyme complex which specifically hydrolyzes RNA residues in RNA-DNA hybrids. RNase H2 substrates may include RNA primers that initiate lagging strand synthesis during DNA replication. Mutations of RNase H2 have been identified in genetic disorders and it is also a putative anti-cancer target. Therefore, a collaboration of UK scientists performed a screen of nearly 49,000 compounds, using the PHERAstar plate reader from BMG LABTECH, in the hopes of identifying RNase H2 inhibitors. Their results were published in  a recent issue of the Journal of Biomolecular Screening.

The key to the assay was designing fluorometric substrates in which a fluorescein labeled oligonucleotide was  annealed to a complementary dabcyl-labeled oligonucleotide which serves as a fluorescence quencher. Substrate degradation leads to release of a fluorescein labeled fragment and consequent increase in fluorescent signal. An RNase H2 selective substrate was designed and inhibitor specificity was confirmed using RNase A and DNase I with their similarly designed selective substrates.

This is just another example of how BMG LABTECH microplate readers are assisting in research around the world!