hnRNP K Supports High-Amplitude D Site-Binding Protein mRNA (Dbp mRNA) Oscillation To Sustain Circadian Rhythms

Mol Cell Biol. 2020 Feb 27;40(6):e00537-19. doi: 10.1128/MCB.00537-19. Print 2020 Feb 27.

Abstract

Circadian gene expression is defined by the gene-specific phase and amplitude of daily oscillations in mRNA and protein levels. D site-binding protein mRNA (Dbp mRNA) shows high-amplitude oscillation; however, the underlying mechanism remains elusive. Here, we demonstrate that heterogeneous nuclear ribonucleoprotein K (hnRNP K) is a key regulator that activates Dbp transcription via the poly(C) motif within its proximal promoter. Biochemical analyses identified hnRNP K as a specific protein that directly associates with the poly(C) motif in vitro Interestingly, we further confirmed the rhythmic binding of endogenous hnRNP K within the Dbp promoter through chromatin immunoprecipitation as well as the cycling expression of hnRNP K. Finally, knockdown of hnRNP K decreased mRNA oscillation in both Dbp and Dbp-dependent clock genes. Taken together, our results show rhythmic protein expression of hnRNP K and provide new insights into its function as a transcriptional amplifier of Dbp.

Keywords: Dbp; circadian rhythm; hnRNP K; mRNA oscillation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Animals
  • Cell Line
  • Circadian Rhythm / genetics*
  • DNA-Binding Proteins / genetics*
  • HEK293 Cells
  • Heterogeneous-Nuclear Ribonucleoprotein K / genetics*
  • Humans
  • Mice
  • Poly C / genetics
  • Promoter Regions, Genetic / genetics*
  • RNA Interference
  • RNA, Messenger / genetics
  • RNA, Small Interfering / genetics
  • Transcription Factors / genetics*
  • Transcriptional Activation / genetics*

Substances

  • DBP protein, human
  • DNA-Binding Proteins
  • Heterogeneous-Nuclear Ribonucleoprotein K
  • RNA, Messenger
  • RNA, Small Interfering
  • Transcription Factors
  • HNRNPK protein, human
  • Poly C