Distinct Roles of DBHS Family Members in the Circadian Transcriptional Feedback Loop

Abstract

Factors interacting with core circadian clock components are essential to achieve transcriptional feedback necessary for metazoan clocks. Here, we show that all three members of the Drosophila behavior human splicing (DBHS) family of RNA-binding proteins play a role in the mammalian circadian oscillator, abrogating or altering clock function when overexpressed or depleted in cells. Although these proteins are members of so-called nuclear paraspeckles, depletion of paraspeckles themselves via silencing of the structural noncoding RNA (ncRNA) Neat1 did not affect overall clock function, suggesting that paraspeckles are not required for DBHS-mediated circadian effects. Instead, we show that the proteins bound to circadian promoter DNA in a fashion that required the PERIOD (PER) proteins and potently repressed E-box-mediated transcription but not cytomegalovirus (CMV) promoter-mediated transcription when they were exogenously recruited. Nevertheless, mice with one or both copies of these genes deleted show only small changes in period length or clock gene expression in vivo. Data from transient transfections show that each of these proteins can either repress or activate, depending on the context. Taken together, our data suggest that all of the DBHS family members serve overlapping or redundant roles as transcriptional cofactors at circadian clock-regulated genes.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00334-12.

ACKNOWLEDGMENTS

We thank Robert Dallmann for a critical reading of the manuscript and W. Schaffner (University of Zurich) for donation of Gal4 vectors.

This work was supported by the Swiss National Science Foundation and the University of Zurich Fonds der Akademischen Nachwuchses. Further support to S.A.B. was provided by the Neurosciences Center Zurich and the Molecular Life Sciences programs.