Authors
Mei-Chin Lee, Ling-Ling Toh, Lai-Ping Yaw and Yan Luo.

Abstract
We reveal a set of divergent octamer elements in Drosophila melanogaster (dm) core histone gene promoters. These elements recruit transcription factor POU-domain protein in D. melanogaster 1 (Pdm-1), which along with co-activator dmOct-1 CoActivator in S-phase (dmOCA-S) activates transcription from at least the Drosophila histone 2B (dmH2B) and 4 (dmH4) promoters in a fashion similar to the transcription of mammalian histone 2B (H2B) gene activated by octamer binding transcription factor 1 (Oct-1) and Oct-1 CoActivator in S-phase (OCA-S). The expression of core histone genes in both kingdoms is coordinated; however, while the expression of mammalian histone genes involves subtype-specific transcription factors and/or co-activator(s), the expression of Drosophila core histone genes is regulated by a common module (Pdm-1/dmOCA-S) in a directly coordinated manner. Finally, dmOCA-S is recruited to the Drosophila histone locus bodies (HLB) in the S-phase, marking S-phase-specific transcription activation of core histone genes.

Figure Legend: dmOCA-S is recruited to Drosophila Histone Locus Bodies during S phase. (A) A transcriptional regulation pathway of D. melanogaster core histone genes. All the core histone genes contain multiple octamer sites in their promoters for recruitment of the common transcription factor Pdm-1, which in turn recruits dmOCA-S that might well be the universal co-activator for the coordinated expression of all Drosophila core histone genes. (B-E) Random cells images. (F) Cell cycle profiles of random cells; ~20% of the cells were in the S-phase. A similar percentage was obtained when counting 100 randomly picked cells using HLB-foci-staining as a criterion. (G-J) Early S-phase cells images that show weak HLB foci and co-localization with nuclear dmGapdh. (K) Early S-phase cell cycle profiles. (L-O) Mid-S-phase cells images that show prominent HLB foci with strong co-localization with nuclear dmGapdh foci. (P) Mid-S-phase cell cycle profiles. (Q-T) Late S- and early G2-phase cells images that show decreased nuclear dmGapdh and HLB foci in size and number. (U) Late S- and early G2-phase cell cycle profiles. (V-Y) G2-phase cells, with no HLB and dmGapdh nuclear foci. (Z) G2-phase cell cycle profiles. When appropriate, arrows indicate HLB (B, G, L, Q, V) and nuclear dmGapdh (C, H, M, R, W) foci and their nuclear co-localization (D, I, N, S, X), which was confirmed by superimposing to DAPI nuclei-staining images (E, J, O, T, Y). HLB foci were stained with the MPM-2 antibody; nuclear dmGapdh foci were stained by anti-p38/GAPDH antibodies. Bar, 10 μM.

Published in the Journal of Biological Chemistry:
http://www.jbc.org/content/early/2010/01/22/jbc.M109.075358.full.pdf+html

For more information on Prof. Yan Luo's Lab, please click here.