The "Mutated in Colorectal Cancer" Protein Is a Novel Target of the UV-Induced DNA Damage Checkpoint

Abstract

MCC is a potential tumor suppressor gene, which is silenced by promoter hypermethylation in a subset of colorectal cancers. However, its functions have remained poorly understood. In the present study, we describe a novel function of MCC in the DNA damage response. Several novel phosphorylation sites were identified by mass spectrometry, including 2 highly conserved ATM/ATR consensus sites at serine 118 and serine 120. In addition, exposure to ultraviolet radiation (UV), but not phleomycin, caused PI3K-dependent phosphorylation of MCC and its nuclear localization. Re-expression of MCC in HCT15 colorectal cancer cells led to a G2/M arrest, and MCC knockdown impaired the induction of a G2/M arrest following UV radiation. Finally, mutation of S118/120 to alanine did not affect MCC nuclear shuttling following UV but did impair MCC G2/M checkpoint activity. Thus, these results suggest that MCC is a novel target of the DNA damage checkpoint and that MCC is required for the complete cell cycle arrest in the G2/M phase in response to UV.

The PDZ domain protein Mcc is a novel effector of non-canonical Wnt signaling during convergence and extension in zebrafish

“…In addition, Mcc localizes to the leading edge of polarized cells and interacts in a PDZ-independent manner with the contractile protein myosin IIB (Pangon et al, 2012). Knockdown of MCC impairs lamellipodia formation and cell migration in Boyden chamber assays (Arnaud et al, 2009;Pangon et al, 2010Pangon et al, , 2012. Lastly, we recently observed enriched MCC expression in a microarray screen comparing the differentiation of human embryonic stem cells in response to combinations of TGFβ-related growth factors (Teo et al, 2012).…”

“…In overexpression studies, MCC was shown to physically associate with β-catenin in the nucleus to negatively regulate canonical TCF/ LEF-dependent Wnt signaling and to inhibit cell proliferation (Fukuyama et al, 2008;Matsumine et al, 1996). More recently, MCC was observed to be mainly localized in the cytoplasm of colon cancer cell lines but translocated to the nucleus in response to DNA damage to induce cell cycle arrest (Pangon et al, 2010). These findings are consistent with the frequent hypermethylation (and gene silencing) of the MCC promoter in human CRCs (Kohonen-Corish et al, 2007).…”

“…Lastly, serine phosphorylation of MCC has been observed at residues 115, 118 and 120 and also at amino acid 827 (position −1) within the C-terminal ETSL PDZ interaction domain (Pangon et al, 2010(Pangon et al, , 2012. We generated several versions of mouse Mcc isoform 2 in which these serine residues were mutated to non-phosphorylatable alanine to address the requirement of phosphorylation for Mcc function (supplementary material Fig.…”

“…Immunolocalization studies in a variety of cell types show that MCC is principally a cytoplasmic protein (Fukuyama et al, 2008;Matsumine et al, 1996;Pangon et al, 2010;Senda et al, 1999). We determined the subcellular distribution of Mcc in the gastrulating zebrafish embryo by injecting mRNA encoding an N-terminal GFP-Mcc fusion protein and imaging GFP fluorescence at shield stage.…”

Loss of heterozygosity of the Mutated in Colorectal Cancer gene is not associated with promoter methylation in non-small cell lung cancer

“…In addition to regulating cell proliferation in many cancer cell lines [17,26], it has been suggested that MCC is involved in differentiation [27], epithelial cell migration [28,29], DNA damage response [30] and inhibition of NFB activation [31,32] or Wnt signalling [17]. Importantly, the tumour suppressor role of MCC has been confirmed in a mouse model of colon cancer [33].…”