The first library we constructed and screened in this work (lib1) was composed of potential H3K27-trimethylation biosensors containing a variety of different binding domains. Among the binding domains included in this library were three engineered variants that have been developed in our lab and not previously reported elsewhere: JMJD2A double tudor domain [1,2] with D945K; JMJD2A double tudor domain with the D945R; and Cbx7 chromodomain  with A71K. These variants are the result of a research project aimed at using phage display-based screening for the development of improved reagents for molecular recognition of trimethylated H3K27. However, due to the relatively modest gains in specificity in these engineered variants, this work was not pursued further. This document describes the identification of these variants.