1990 1991 Postdoctoral Fellow, Microbiology and Molecular Genetics, Harvard Medical School
1991-1992 Research Associate, Microbiology and Molecular Genetics, Harvard Medical School
1983 1985 Lecturer, Suwon University
1992-1994 Instructor, Microbiology and Molecular Genetics, Harvard Medical School
1994-1998 Assistant Professor of Microbiology and Molecular Genetics, Harvard Medical School
1995-2007 Member, Biological and Biochemical Science, Harvard Medical School
1999-2003 Associate Professor of Microbiology and Molecular Genetics, Harvard Medical School
1999-2007 Chairman of Tumor Virology Division, New England Primate Research Center (NEPRC), Harvard Medical School
2001-2008 Adjunct Associate Professor, Department of Microbiology and Molecular Genetics, University of Massachusetts Medical School
2004-2007 Tenured Professor of Microbiology and Molecular Genetics, Harvard Medical School
2006-present Adjunct Professor of Department of Life Science, POSTECH, Korea.
2007-present Adjunct Professor of Department of Biology, KAIST, Korea.
2008-present Visiting Professor of Microbiology and Molecular Genetics, Harvard Medical School
2008-present Distinguished Professor
Chairman of Molecular Microbiology and Immunology department,
Director of USC Institute of Emerging Pathogens and Immune Diseases Keck Medical School
Professor of Pharmacology and Pharmaceutical Sciences Department School of Pharmacy
Professor of Molecular and Computational Biology Department College of Letters, Arts and Sciences University of Southern California
University of Southern California: Los Angeles, CA, US 2008-01-01 to present , professor
University of Southern California: Los Angeles, CA, US 2008-01-01 to present ,chair (molecular microbiology and immunology)