Soo-Jong Um

Inactivation of Interferon Regulatory Factor-1 Tumor Suppressor Protein by HPV E7 Oncoprotein IMPLICATION FOR THE E7-MEDIATED IMMUNE EVASION MECHANISM IN CERVICAL CARCINOGENESIS

In studying biological roles of interferon regulatory factor (IRF)-1 tumor suppressor in cervical carcinogenesis, we found that HPV E7 is functionally associated with IRF-1. Binding assays indicate a physical interaction between IRF-1 and HPV E7in vivo and in vitro. The carboxyl-terminal transactivation domain of IRF-1 was required for the interaction. Transient co-expression of E7 significantly inhibits the IRF-1-mediated activation of IFN-β promoter in NIH-3T3 cells. Co-transfection of E7 mutants reveals that the pRb-binding portion of E7 is necessary for the E7-mediated inactivation of IRF-1. It was next determined whether histone deacetylase (HDAC) is involved in the inactivation mechanism as recently suggested, where the carboxyl-terminal zinc finger domain of E7 associates with NURD complex containing HDAC. When trichostatin A, an inhibitor of HDAC, was treated, the repressing activity of E7 was released in a dose-dependent manner. Furthermore, the mutation of zinc finger abrogates such activity without effect on the interaction with IRF-1. These results suggest that HPV E7 interferes with the transactivation function of IRF-1 by recruiting HDAC to the promoter. The immune-promoting role of IRF-1 evokes the idea that our novel finding might be important for the elucidation of the E7-mediated immune evading mechanism that is frequently found in cervical cancer.

Reciprocal roles of SIRT1 and SKIP in the regulation of RAR activity: implication in the retinoic acid-induced neuronal differentiation of P19 cells

Human sirtuin 1 (SIRT1) is a NAD+-dependent deacetylase that participates in cell death/survival, senescence and metabolism. Although its substrates are well characterized, no direct regulators have been defined. Here, we show that SIRT1 associates with SKI-interacting protein (SKIP) and modulates its activity as a coactivator of retinoic acid receptor (RAR). Binding assays indicated that SKIP interacts with RAR in a RA-dependent manner, through a region that overlaps the binding site for SIRT1. SKIP augmented the transcriptional activation activity of RAR by cooperating with SRC-1, and SIRT1 suppressed SKIP/SRC-1-enhanced RAR transactivation activity. The suppression was dependent on the deacetylase activity of SIRT1 and was enhanced by a SIRT1 activator, resveratrol. In contrast, the suppression was relieved by SIRT1 knockdown, overexpression of SKIP and treatment with a SIRT1 inhibitor, splitomicin. Upon SKIP overexpression, the recruitment of SIRT1 to the endogenous RARβ2 promoter was severely impaired, and SKIP was recruited to the promoter instead. Finally, resveratrol treatment inhibited RA-induced neuronal differentiation of P19 cells, accompanied by reductions in the neuronal marker nestin and a RAR target gene, RARβ2. This inhibition was relieved by either knockdown of SIRT1 or overexpression of SKIP. These data suggest that SIRT1 and SKIP play reciprocal roles in the regulation of RAR activity, which is implicated in the regulation of RA-induced neuronal differentiation of P19 cells.

Responses of periodontal ligament stem cells on various titanium surfaces

OBJECTIVE Periodontal ligament has been reported to have adult stem cells (PDLSCs) which are responsible to regenerate the alveolar bone tissue after tooth is removed from its socket. Also PDLSCs may be the stem cells responsible for the osseointegration of titanium implants after installing the implant immediately in the fresh extracted socket. Here we tested cellular responses of PDLSCs on the various titanium surfaces to verify this notion. MATERIALS AND METHODS Titanium disc were prepared for the different surface textures; smooth machined, blasted with 75 and 125 μm Al(2) O(3) particles, and anodized. PDLSCs were cultured on these titanium discs and tested their proliferation and gene expressions of osteocalcin, osteopontin, type I collagen, and GAPDH. RESULTS   Proliferation of PDLSCs was higher on the rough surface blasted with 75 μm Al(2) O(3) particles. Osteocalcin expression was increased on the Al(2) O(3) particle treated-surface regardless of its particle size. Type I collagen expression was generally decreased with time in 6 days culture. CONCLUSIONS In this experiment, it was shown that cultured PDLSCs proliferate in higher rate on the rough surface especially at the 75 μm Al(2) O(3) particle treated surface than other surfaces. Also, osteocalcin was highly expressed on the rough surfaces treated with 75 μm and 125 μm Al(2) O(3) particles.

Effects of BMP-2 on the osteogenic differentiation of bone marrow stem cells in fibrous dysplasia

OBJECTIVES The purpose of this study was to evaluate the effects of BMP-2 on bone-grafting procedures for the treatment of fibrous dysplasia based on in vitro and in vivo experiments. SUBJECTS AND METHODS Proliferation of stem cells was determined by colony-forming assay, CCK-8 assay and BrdU staining. OCT4 and NANOG expression was analysed by flow cytometry and immunocytochemistry. Osteogenic differentiation was assessed by measuring ALP activity, Alizarin red S staining and in vivo transplantation. Gene expression of the osteogenic markers, osteocalcin and type 1 collagen, was determined by RT-PCR. RESULTS FD-BMSCs showed few calcium deposits and low ALP activity. Bone formation by transplanted FD-BMSCs was also suppressed relative to that of normal BMSCs. However, BMP-2 treatment enhanced osteogenic differentiation of FD-BMSCs mixed with normal BMSCs in vitro and in vivo. Overall, BMP-2 treatment promoted osteogenic differentiation of FD-BMSCs mixed with normal BMSCs. CONCLUSIONS In patients with FD, stem cells in affected bone are influenced by the mutation, resulting in weak bone formation with the proliferation of immature osteogenic cells. Current treatment of FD involves surgical removal of excess bulk lesions, which can cause facial disfigurement. Our results suggest that BMP-2 application is a good adjunctive modality to the surgical treatment of patients with FD.