GSE112265
MKL1 augments megakaryocyte maturation by enhancing the SRF regulatory axis [ChIP-seq]
SRF is a ubiquitous transcription factor that binds DNA in association with myocardin-family proteins (e.g. MKL1), or the ternary complex factor (TCF) family of ETS proteins. In primary hematopoietic cells, knockout of either SRF or MKL1 decreases megakaryocyte maturation caused thrombocytopenia, and MKL1 over-expression (MKL1OE) in the Human Erythroleukemia (HEL) cell line enhances megakaryopoiesis, but the mechanisms underlying these effects are unknown. To elucidate the role of SRF and MKL1 in megakaryopoiesis, integrated analysis was performed of anti-SRF ChIP-seq and RNA-seq data in undifferentiated and differentiated HEL cells, both with and without induction of MKL1OE. MKL1OE enhances TPA-induced megakaryopoiesis with 25% of genes upregulated, as opposed to 11% with TPA alone. MKL1OE increases SRF binding to genomic sites, and enhances expression of specific target cytoskeletal genes in response to TPA.  Genes upregulated in response to TPA are predicted to be regulated by SRF and ETS factors, whereas those upregulated in TPA plus MKL1OE lack ETS binding motifs. Using ChIP-PCR, we validated that both SRF and MKL1 have increased binding at target upregulated genes, e.g. CORO1A, with MKL1OE. We show for the first time that MKL1 increases both the genomic association and activity of SRF, and upregulates genes that enhance megakaryopoiesis. Overall design: 4 treatment groups of HEL-iMKL1 cells were studied for anti-SRF ChIP-seq: untreated, Dox-treated (MKL1^OE), TPA-treated (TPA+), and Dox+TPA-treated (TPA+MKL1^OE).  Two replicates of each type were used.