| Summary: | 碩士 === 高雄醫學大學 === 醫學研究所 === 98 === Human cytomegalovirus (HCMV) UL112-113 is one of essential genes involved in viral genome oriLyt-dependent replication. Previous reports have shown that UL112-113 encodes four phosphoproteins, p34, p43, p50, and p84. Recently, three novel proteins p20, p26, and p28 are identified, Additionally, Dr. Wang and students showed that protease inhibitors reduced the levels of these three novels proteins. Taken together these results, we suggested that these novel proteins are most likely derived form cellular proteolytic modification. We further noticed that proteins encoded by UL112-113 contain significant PEST motif by using a ePESTfind program. Recent studies have revealed that degradation of PEST-containing proteins is mediated by three molecular pathways: ubiquitin-proteasome system, calpain and caspase. Therefore, this study aimed to investigate the pathways involved in the protein degradation, responsible protease(s) and implications of PEST motif. In this research, protein was produced in prokaryotic system. Highly purified p34 protein was used to identify the specific proteases-mediated these cleavages. We found that calpain and caspase cleaved p34 (contain PEST region). However, only caspase cleaved p28 (with deletion in PEST region). Therefore, calpain recognized PEST motif for cleavage. Caspase recognizes specific sequence for cutting.
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