Regulation of Hox Gene Activity by Transcriptional Elongation in Drosophila

• Published in: Current biology Vol. 19; no. 8; pp. 688 - 693
• Main Authors: Chopra, Vivek S., Hong, Joung-Woo, Levine, Michael
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 28.04.2009
• Subjects: Animals; Body Patterning - genetics; Cyclin-Dependent Kinase 9 - genetics; Cyclin-Dependent Kinase 9 - metabolism; DEVBIO; DNA; Drosophila; Drosophila melanogaster - anatomy & histology; Drosophila melanogaster - embryology; Drosophila melanogaster - genetics; Drosophila melanogaster - metabolism; Drosophila Proteins - genetics; Drosophila Proteins - metabolism; Gene Expression Regulation, Developmental; Genes, Homeobox; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; Metazoa; Mutation; Phenotype; Promoter Regions, Genetic; Transcription Factors - genetics; Transcription Factors - metabolism; Transcription, Genetic; Transcriptional Elongation Factors - genetics; Transcriptional Elongation Factors - metabolism; Wings, Animal - anatomy & histology; Wings, Animal - embryology; DNA; DEVBIO
• ISSN: 0960-9822; 1879-0445; 1879-0445
• DOI: 10.1016/j.cub.2009.02.055

Hox genes control the anterior-posterior patterning of most metazoan embryos. Their sequential expression is initially established by the segmentation gene cascade in the early Drosophila embryo [1]. The maintenance of these patterns depends on the Polycomb group (PcG) and trithorax group (trxG) complexes during the remainder of the life cycle [2]. We provide both genetic and molecular evidence that the Hox genes are subject to an additional tier of regulation, i.e., at the level of transcription elongation. Both Ultrabithorax (Ubx) and Abdominal-B (Abd-B) genes contain stalled or paused RNA polymerase II (Pol II) even when silent [3, 4]. The Pol II elongation factors Elongin-A and Cdk9 are essential for optimal Ubx and Abd-B expression. Mitotic recombination assays suggest that these elongation factors are also important for the regulation of Notch-, EGF-, and Dpp-signaling genes. Stalled Pol II persists in tissues where Ubx and Abd-B are silenced by the PcG complex. We propose that stalling fosters both the rapid induction and precise silencing of Hox gene expression during development.