NF-κB subunit RELA suppression of mucosa-associated lymphoid tissue lymphoma translocation protein 1 expression in oral carcinoma cells.

Loss of mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) expression closely associates with increased aggressive behaviors of oral carcinoma cells. It emphasizes that a mechanism to suppress the expression is an important subject for understanding carcinoma progression pathway. However, nothing is known at present. This study conducted on transcriptional regulation of the gene down-regulation. Reporter assays showed the presence of the silencer region between +402 and +501 region of MALT1 gene in oral carcinoma cells. It encoded a binding site of nuclear factor-κB subunit, RELA. RELA binding to the site was confirmed by the chromatin immunoprecipitation analyses, and deletion and mutations of the site significantly decreased the RELA binding. Short interfering RNAs for RELA up-regulated reporter gene and endogenous MALT1 protein expressions, and deletion and mutations of RELA binding site increased reporter gene expression. These results demonstrated RELA-binding to the site suppresses MALT1 expression that may facilitate oral carcinoma progression.

Domain structures of mucosa-associated lymphoid tissue lymphoma translocation 1 protein for nuclear localization in oral carcinoma cells and the proliferation inhibition.

Mucosa-associated lymphoid tissue lymphoma translocation 1 protein (MALT1) consisting of death domain, Ig-like domains and caspase-like domain is expressed in nucleus of oral carcinoma cells, and loss of the expression closely associates with disease progression and stimulates proliferation of the cells. However, nothing is known about the molecular backgrounds. In this study, eight constructs with different domain constitution of human MALT1 and six constructs were transiently and stably transfected into oral carcinoma cell lines, respectively. The immunoblot analysis showed that constructs containing caspase-like domain was expressed in nucleus and the domain-deleted constructs in cytoplasm. Immunocytochemistry of stably transfected HSC2 oral carcinoma cells confirmed the caspase-like domain-dependent nuclear localization. Involvement of domains in proliferation of stably transfected HSC2 cells was quantified by the real-time and conventional colorimetric assays. In contrast to suppression of the proliferation by full-length wild-type MALT1, any domain-deleted constructs enhanced the proliferation. Death domain construct without caspase-like domain suppressed the proliferation when it was localized in nucleus by ligating with the nuclear localization signal. These results demonstrate that nuclear localization of MALT1 in oral carcinoma cells depends on the presence of caspase-like domain and that death domain nuclear entity is responsible for MALT1 inhibition of oral carcinoma cell proliferation. Nuclear localization of death domain led by caspase-like domain may suppress oral carcinoma progression.

Hmga2 regulation of tooth formation and association with Sox2 and Nanog expression.

Tooth formation is accomplished under strict genetic programs. Although patients with chromosome 12q14 aberration shows tooth phenotype including the size and eruption timing with bone growth anomaly, its etiology is uncertain. Here, we examined expression of Hmga2, which is encoded at chromosome 12q14, in mouse tooth germs and analyzed the involvement in lower first molar (M1) and mandibular bone development. Hmga2 expression was immunohistochemically detected at enamel organ and the surrounding mesenchyme of the M1 germs. The expression was dynamically changed with gestation and rapidly decreased in postnatal mice. In Hmga2-/- mice, the M1 germs and crowns were diminished in size, and formation and eruption of molars were delayed with mandibular bone growth retardation. Hmga2 cDNA or siRNA transfection showed that Hmga2 transcriptionally up-regulates expression of stem cell factors, Sox2 and Nanog. They were co-localized with Hmga2 in the germs, but differentially distributed at enamel organ and mesenchyme in Hmga2-/- mice. These results demonstrate that Hmga2 expressed in tooth germs regulates the growth, sizing and eruption and stem cell factor expression in different compartment of the germ and associates with mandibular bone growth. Although future studies are needed, the present study demonstrates HMGA2 regulation of tooth genesis with skeletal development.