The MUC1 heterodimeric transmembrane glycoprotein is aberrantly overexpressed by diverse human carcinomas. Galectin-3 is a beta-galactoside binding protein that has also been associated with the development of human cancers. The present results demonstrate that MUC1 induces galectin-3 expression by a posttranscriptional mechanism. We show that the MUC1 C-terminal subunit is glycosylated on Asn-36 and that this modification is necessary for upregulation of galectin-3. N-glycosylated MUC1-C increases galectin-3 mRNA levels by suppressing expression of the microRNA miR-322 and thereby stabilizing galectin-3 transcripts. The results show that, in turn, galectin-3 binds to MUC1-C at the glycosylated Asn-36 site. The significance of the MUC1-C-galectin-3 interaction is supported by the demonstration that galectin-3 forms a bridge between MUC1 and the epidermal growth factor receptor (EGFR) and that galectin-3 is essential for EGF-mediated interactions between MUC1 and EGFR. These findings indicate that MUC1 and galectin-3 function as part of a miR-322-dependent regulatory loop.

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Tle1 (transducin-like enhancer of split 1) is a corepressor that interacts with a variety of DNA-binding transcription factors and has been implicated in many cellular functions; however, physiological studies are limited. Tle1-deficient (Tle1 Δ/Δ ) mice, although grossly normal at birth, exhibit skin defects, lung hypoplasia, severe runting, poor body condition, and early mortality. Tle1 Δ/Δ mice display a chronic inflammatory phenotype with increased expression of inflammatory cytokines and chemokines in the skin, lung, and intestine and increased circulatory IL-6 and G-CSF, along with a hematopoietic shift toward granulocyte macrophage progenitor and myeloid cells. Tle1 Δ/Δ macrophages produce increased inflammatory cytokines in response to Toll-like receptor (TLR) agonists and lipopolysaccharides (LPS), and Tle1 Δ/Δ mice display an enhanced inflammatory response to ear skin 12-O-tetradecanoylphorbol-13-acetate treatment. Loss of Tle1 not only results in increased phosphorylation and activation of proinflammatory NF-κB but also results in decreased Hes1 (hairy and enhancer of split-1), a negative regulator of inflammation in macrophages. Furthermore, Tle1 Δ/Δ mice exhibit accelerated growth of B6-F10 melanoma xenografts. Our work provides the first in vivo evidence, to our knowledge, that TLE1 is a major counterregulator of inflammation with potential roles in a variety of inflammatory diseases and in cancer progression.T ransducin-like enhancer of split 1 (TLE1) belongs to a family of corepressor proteins called transducin-like enhancer of split, or TLEs. Groucho, the TLE homolog in Drosophila, has crucial roles in neurogenesis, segmentation, and sex determination (1). These corepressors do not bind directly to DNA but rather interact with many different classes of transcription factors and help create a repressor complex (1, 2).Vertebrates express five different TLEs (TLE1-4, AES), although the distinct functions of each of the TLEs has not been well determined. TLE1, the most studied among the Groucho family proteins in mammalian systems, is widely expressed in different tissues and cell types and has been implicated in neuronal differentiation (3, 4) and pancreatic beta cell development (5). TLE1 has tumor suppressor activity (6-8) as well as oncogenic functions in cancer (9, 10). TLE1 associates with many important transcription factors integral for cell proliferation and differentiation, including Runx2 to block rRNA expression (11), HES1 to suppresses MASH2 expression (12), and TCF/LEF proteins to block Wnt target gene activation (13). TLE1 also represses NF-κB activity (14,15). Involvement in these diverse cellular functions and diseases was studied primarily in vitro or using in vivo overexpression systems. The major physiological function of TLE1, however, remains poorly understood.A few recent studies suggest TLE1 might regulate immune function. For example, a single noncoding nucleotide polymorphism within the TLE1 locus was associated with inflammatory bowel diseases (16), and in human monocytes,...