Sung-Jen Wei
Assistant Professor
Ph.D., National Defense Medical Center (Taiwan)
Office: 956-393-6429
Email: WeiS3@uthscsa.edu
Keywords
keratinocyte stem cells, skin carcinogenesis, DSS1, RPN3/S3, ubiquitin-proteasome system, protein degradation, p53
Research Summary
The goals of our studies are to identify novel genes involved in early skin neoplastic development using a Tg.AC mouse model. This model possesses a v-Ha-ras transgene under the regulation of a fetal zeta-globin gene promotor which confers a unique phenotype of inducible skin papillomas with a high rate of progression to invasive squamous and spindle cell neoplasms. Evidence supports that keratinocyte stem cells (KSCs) residing in the hair follicle bulge region have long been thought to be a major carcinogen target which give rise to the latent neoplastic pool that clonally expand into cutaneous tumors. The candidate integrin alpha6+CD34+ KSCs were isolated using fluorescence-activated cell sorting from hyperplastic skin of TPA-treated Tg.AC mice skins and their gene expression was analyzed using a cDNA microarray. Interestingly, we have identified 11 genes whose expression changed significantly in the TPA-treated integrin alpha6+CD34+ KSCs. Two up-regulated genes, DSS1 and NDPK-B, have been identified and characterized as critical TPA-inducible genes expressed in KSCs, with possible involvement in early skin carcinogenesis. Recently, our laboratory is interested in the roles of DSS1 played by the ubiquitin-proteasome system in regulating protein degradation functions. We demonstrated that: 1) DSS1 binds to human proteasome via RPN3/S3 subunit of the 19S RP component of the proteasome; 2) the Asp/Glu-rich RPN3/S3-interacting motif of DSS1 regulates proteasome interaction and degradation of ubiquitin-conjugated substrates; 3) the interaction of DSS1 with RPN3/S3 is highly conserved throughout evolution from nematodes to humans; 4) the PCI domain of RPN3/S3 is required for binding to DSS1 and the proteasome; and 5) the DSS1/R3IM-proteasome complex is required for binding and targeting p53 for ubiquitin-mediated protein degradation via gankyrin/HDM2 pathway. Our laboratory is also interested in investigating: 1) if knock down of DSS1 will affect the cell growth and tumor transformation in vitro and in vivo; 2) the DSS1 functions in skin cancer using two-step regimen by conditionally knockout of DSS1 gene in mouse epidermis; 3) the transcriptional regulation by analyzing the binding sites of transcription factors in DSS1 gene promoter region.