Essential role of microphthalmia transcription factor for DNA replication, mitosis and genomic stability in melanoma

Abstract

Malignant melanoma is an aggressive cancer known for its notorious resistance to most current therapies. The basic helix-loop-helix microphthalmia transcription factor (MITF) is the master regulator determining the identity and properties of the melanocyte lineage, and is regarded as a lineage-specific 'oncogene' that has a critical role in the pathogenesis of melanoma. MITF promotes melanoma cell proliferation, whereas sustained supression of MITF expression leads to senescence. By combining chromatin immunoprecipitation coupled to high throughput sequencing (ChIP-seq) and RNA sequencing analyses, we show that MITF directly regulates a set of genes required for DNA replication, repair and mitosis. Our results reveal how loss of MITF regulates mitotic fidelity, and through defective replication and repair induces DNA damage, ultimately ending in cellular senescence. These findings reveal a lineage-specific control of DNA replication and mitosis by MITF, providing new avenues for therapeutic intervention in melanoma. The identification of MITF-binding sites and gene-regulatory networks establish a framework for understanding oncogenic basic helix-loop-helix factors such as N-myc or TFE3 in other cancers.

Identification of a ZEB2-MITF-ZEB1 transcriptional network that controls melanogenesis and melanoma progression

“…Interestingly, MITF-ChIP-seq analysis recently identified the ZEB1 locus as a potential MITF target in human melanoma 501Mel cells (Figure 5f). 39 The specificity of this binding to the ZEB1 locus was confirmed by anti-HA-ChIP-qRT-PCR for both the 5 0 -and 3 0 -end of the gene (Figure 5g). …”

“…ChIP and ChIP-Seq experiments were performed on chromatin from native 501Mel and on 501Mel cells stably expressing 3HA-tagged MITF to standard protocols as previously described. 39 Real-time qPCR analysis. RNA was extracted from cell cultures or ears of 15.5-day-old ZEB2…”

A picture of Mitf in melanoma immortality

“…The paper from Strub et al (2011), arising from a collaboration between the laboratories of Irwin Davidson in Strasbourg, and Robert Ballotti and Corine Bertolotto in Nice, addresses the mechanism underlying Mitf's anti-senescence role. Chromatin immunoprecipitation of HA-tagged Mitf from the 501 mel melanoma cell line followed by high-throughput deep sequencing, together with expression profiling (RNA sequencing) of control and Mitf-depleted cells, revealed the repertoire of genes bound and regulated by Mitf.…”

Microphthalmia‐associated transcription factor regulates skin melanoblast migration by repressing the melanoma cell adhesion molecule

“…Given the multiple target genes MITF regulates in melanocytes, it is not surprising that MITF is also involved in the regulation of MCAM. Nevertheless, most MITF target genes are stimulated by MITF, even though some, such as ZEB1 and SHC4, are apparently suppressed (8,9). Hence, our findings add MCAM to the list of MITF target genes that are negatively regulated by this multifunctional transcription factor.…”