ChIP-seq on Zfp961 GFP flox/flox mESCs to verify Zfp961 binding capacity at PBS-Lys elements.

We performed ChIP-seq assay with anti-GFP antibodies on Zfp961-GFPflox/flox ESCs.We found PBS-Lys-containing endogenous virus K subgroup repeats (ERV-K) were significantly enriched in the strong peak regions (40%, 165 out of 413), compared to their abundance in the mouse genome (~5%), suggesting Zfp961 binding preference towards ERV-K regions. And Zfp961 has a PBS-Lys motif. We performed H3K9me3 ChIP on Zfp961 WT or KO mESCs. We found that Zfp961 recruits H3k9me3 modification at ERVKs, and H3K9me3 level showed a moderate decrease upon Zfp961 deletion. We used two replicates of each ChIP reaction. Basically, two Zfp961-GFP floxed mESCs cell lines treated with 4-OHT or etOH as control were used for anti-GFP ChIP and anti-H3K9me3 ChIP.