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  current news   Press   selected story    
     
  8th September  
  Moonlighting Metabolic Enzymes, Redox Status and Histone Expression
 
 




Authors
Ru-Ping Dai1,3, Fa-Xing Yu1,3, Shuang-Ru Goh1, Hsiao-Wee Chng1, Yan-Li Tan1, Jian-Lin Fu1, Lei Zheng2 and Yan Luo1

1 Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore
2 Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, 1650 Orleans Street, CRB 186, Baltimore, MD 21230, USA
3These authors made equal contributions

Abstract
S-phase transcription of the histone 2B (H2B) gene is dependent on Octamer-binding factor 1 (Oct-1) and Oct-1 Co-Activator in S-phase (OCA-S), a protein complex comprising of glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase (p38/GAPDH and p36/LDH) along with other components. H2B transcription in vitro is modulated by NAD(H). This potentially links the cellular redox status to histone expression. Here, we show that H2B transcription requires a proper NAD+/NADH redox status in vitro and in vivo. Therefore, perturbing a properly balanced redox impairs H2B transcription. A redox-modulated direct p38/GAPDH-Oct-1 interaction nucleates the occupancy of the H2B promoter by the OCA-S complex, in which p36/LDH plays a critical role in the hierarchical organization of the complex. As is p38/GAPDH, p36/LDH is essential for the OCA-S function in vivo, and OCA-S-associated p36/LDH possesses an LDH enzyme activity to impact upon H2B transcription. These studies suggest that the cellular redox status (metabolic states) can directly feedback to gene switching in higher eukaryotes as commonly observed in prokaryotes.


Figure Legend: Histone 2B (H2B) transcription is regulated by moonlighting enzymes p38/GAPDH and p36/LDH, and requires a proper NAD+/NADH redox status.

(A) H2B transcription in vitro is induced by low concentration (0.1-1 mM) but repressed by high dose of NAD+ (2-4 mM).
(B) H2B transcription in vitro is repressed by NADH.
(C) H2B transcription in vitro is impaired, and no longer sensitive to NAD+ or NADH, when p38/GAPDH is depleted.  The inhibitory effect of NADH can be relieved by an enzyme activity of the OCA-S associatedand its substrate pyruvate (Py), which re-oxidizes NADH to NAD+, and the NADH-inhibited H2B transcription cannot be relieved without p36/LDH.
(D) A model depicting the effect of NAD+/NADH redox status on H2B transcription, a redox sensor role of p38/GAPDH, and a redox modulator role of p36/LDH.

Journal of Biological Chemistry, 2008, Epub ahead of print.

For more information on Dr. Yan Luo’s lab, Please Click here.