ZBTB48 is both a vertebrate telomere-binding protein and a transcriptional activator [RNA-seq]

Here we show that ZBTB48 binds directly both to telomeric as well as to subtelomeric variant repeat sequences. ZBTB48 is found at telomeres of human cancer cells regardless of the mode of telomere maintenance and it acts as a negative regulator of telomere length. In addition to its telomeric function, we demonstrate through a combination of RNAseq, ChIPseq and expression proteomics experiments that ZBTB48 acts as a transcriptional activator on a small set of target genes, including mitochondrial fission process 1 (MTFP1). This discovery places ZBTB48 at the interface of telomere length regulation, transcriptional control and mitochondrial metabolism. Overall design: ZBTB48 WT clones were generated by single sorting parental cells (HeLa & U2OS pools) into 96 well plates. ZBTB48 KO clones were generated by transiently transfecting a ZBTB48 TALEN pair (H12250; from TALEN library Resource, Seoul National University) into HeLa and U2OS cells, followed by single sorting into 96 well plates. Clones were first phenotypically screened for absence of ZBTB48 IF staining and subsequently verified by sequencing the exact genomic alterations across the TALEN cut site. Counts provided are not normalized.