SUMOylation of FOXM1B alters its transcriptional activity on regulation of MiR-200 family and JNK1 in MCF7 human breast cancer cells.

Chiung-Min Wang,Wei-Hsiung Yang,Victoria Brennan,Runhua Liu,Leticia Nascimento,Lizhong Wang

doi:10.3390/ijms150610233

Abstract

Transcription factor Forkhead Box Protein M1 (FOXM1) is a well-known master regulator in controlling cell-cycle pathways essential for DNA replication and mitosis, as well as cell proliferation. Among the three major isoforms of FOXM1, FOXM1B is highly associated with tumor growth and metastasis. The activities of FOXM1B are modulated by post-translational modifications (PTMs), such as phosphorylation, but whether it is modified by small ubiquitin-related modifier (SUMO) remains unknown. The aim of the current study was to determine whether FOXM1B is post-translationally modified by SUMO proteins and also to identify SUMOylation of FOXM1B on its target gene transcription activity. Here we report that FOXM1B is clearly defined as a SUMO target protein at the cellular levels. Moreover, a SUMOylation protease, SENP2, significantly decreased SUMOylation of FOXM1B. Notably, FOXM1B is selectively SUMOylated at lysine residue 463. While SUMOylation of FOXM1B is required for full repression of its target genes MiR-200b/c and p21, SUMOylation of FOXM1B is essential for full activation of JNK1 gene. Overall, we provide evidence that FOXM1B is post-translationally modified by SUMO and SUMOylation of FOXM1B plays a functional role in regulation of its target gene activities.

Highlights

Forkhead Box Proteins (FOX proteins) are transcription factors consisting of more than 55 mammalian proteins and sharing a 100-amino acid long, evolutionarily conserved winged helixDNA-binding region [1]
We demonstrated that Forkhead Box Protein M1 B (FOXM1B) is a substrate for small ubiquitin-related modifier (SUMO) modification and FOXM1B transcriptional activity requires conjugating of SUMO to mediate efficient SUMOylation of FOXM1B at lysine 463
To determine whether FOXM1B can be SUMOylated by SUMO1 in mammalian cells, MCF7 breast cancer and H1299 lung cancer cells were transiently transfected with HIS-FLAG tagged FOXM1B expression plasmids with or without HA-tagged SUMO1 (WT or AA mutant) expression plasmids

Summary

Introduction

Forkhead Box Proteins (FOX proteins) are transcription factors consisting of more than 55 mammalian proteins and sharing a 100-amino acid long, evolutionarily conserved winged helixDNA-binding region [1]. FOXM1 (previously known as FKHL16, HFH11, and MPP2) plays a crucial role in the regulation of cell cycle progression and cell proliferation [2,3,4,5]. FOXM1 is regulated by numerous oncogenic signals, growth factors, p53, pRb, p19ARF, and itself (by auto-regulation) [6,7,8,9,10,11]. For adherens junctions and cell self-renewal, CDKN1A [15] for cell proliferation, VEGF [16] for blood vessel formation, MMP2 [17] and JNK1 [18] for cell migration, HELLS [19] and SKP2 [20] for cell cycle regulation, and NR3A1 [21] for estrogen signaling in humans by binding to promoter regions with a preference for a conserved consensus 5'-TAAACA-3' sequence.

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