a, Schematic representation of the STARR-seq cloning and screening strategy in K-562 cells. BACs available for the extended MYC locus (covering approximately 91% of a 3.1 Mb region at the MYC locus) and 25 genic control BACs were fragmented and cloned into a modified STARR-seq vector containing a minimal MYC promoter. This library was then screened for enhancer activity using STARR-seq in K-562 cells with or without 250 nM JQ1. The schematic shows the underlying principle of STARR-seq: a bona fide enhancer can activate its own transcription from a minimal MYC promoter. Messenger RNA corresponding to active enhancer elements will therefore become more abundant among the cellular RNA compared to inactive fragments. b, PVT1 mRNA levels (RPKM) at different time points after JQ1 treatment (200 nM) in indicated cell lines, relative to levels in DMSO-treated cells. PVT1 expression is generally reduced upon JQ1 treatment indicating no association with enhancer activation.