Promoter Frame Position Affects Strength and Nature of Circadian Oscillations in hPER2 Luciferase Reporters

The <i>PER2</i> gene is a crucial component responsible for the proper functioning of the mammalian core circadian clock. The circadian nature of the murine <i>Per2</i> (<i>mPer2</i>) promoter's activity has been thoroughly investigated to identify important elements responsible for its oscillatory behavior; however, its human counterpart has not. While there are similarities between murine and human core clocks, there are differences and unconserved elements between their promoter sequences that may influence the nature of rhythms. Further, most studies to date have used murine-based sequences in human cell lines. To fully understand the role(s) of and factors involved in the human <i>PER2</i> (<i>hPER2</i>) gene, human-derived sequences should be used. To this end, we developed two lentiviral luciferase reporters in well-established, circadian model U2OS cells using different <i>hPER2</i> promoter regions. Their rhythmic nature was compared to that of the standard <i>mPer2</i> promoter reporter. We found that <i>hPER2</i> reporters exhibited stronger oscillations than the <i>mPer2</i> reporter, and that the frame of the <i>hPER2</i> promoter affected the period and phase. This work introduces a human sequence-based <i>PER2</i> promoter in U2OS cells, which should be used for further in vitro tracking of <i>hPER2</i> activity and to understand <i>PER2</i> gene dynamics, in lieu of the murine iteration.