Transcription defines the embryonic domains of cis-regulatory activity at the Drosophila bithorax complex

The extensive infraabdominal (iab) region contains a number of cis-regulatory elements, including enhancers, silencers, and insulators responsible for directing the developmental expression of the abdominal-A and Abdominal-B homeotic genes at the Drosophila bithorax complex. It is unclear how these regulatory elements are primed for activity early in embryogenesis, but the 100-kb intergenic region is subject to a complex transcriptional program. Here, we use molecular and genetic methods to examine the functional activity of the RNAs produced from this region and their role in cis regulation. We show that a subset of these transcripts demonstrates a distinct pattern of cellular localization. Furthermore, the transcripts from each iab region are discrete and the transcripts do not spread across the insulator elements that delineate the iab regions. In embryos carrying a Mcp deletion, the intergenic transcription pattern is disrupted in the iab4 region and the fourth abdominal segment is transformed into the fifth. We propose that intergenic transcription is required early in embryogenesis to initiate the activation of the Drosophila bithorax complex and define the domains of activity for the iab cis-regulatory elements. We also discuss a possible mechanism by which this may occur.

[1]  F. Karch,et al.  A new homeotic mutation in the Drosophila bithorax complex removes a boundary separating two domains of regulation. , 1990, The EMBO journal.

[2]  P. Geyer,et al.  The role of insulator elements in defining domains of gene expression. , 1997, Current opinion in genetics & development.

[3]  D. Tuan,et al.  Transcription of the HS2 enhancer toward a cis-linked gene is independent of the orientation, position, and distance of the enhancer relative to the gene , 1997, Molecular and cellular biology.

[4]  B. Bainbridge,et al.  Genetics , 1981, Experientia.

[5]  F. Karch,et al.  The bluetail transposon: evidence for independent cis‐regulatory domains and domain boundaries in the bithorax complex. , 1993, The EMBO journal.

[6]  A. Udvardy,et al.  Genetic and molecular analysis of chromatin domains. , 1993, Cold Spring Harbor symposia on quantitative biology.

[7]  E. Sánchez-Herrero,et al.  Spatially ordered transcription of regulatory DNA in the bithorax complex of Drosophila. , 1989, Development.

[8]  F. Karch,et al.  Transcription through the iab-7 cis-regulatory domain of the bithorax complex interferes with maintenance of Polycomb-mediated silencing. , 2002, Development.

[9]  V. Pirrotta,et al.  Polycombing the Genome: PcG, trxG, and Chromatin Silencing , 1998, Cell.

[10]  P. Fraser,et al.  Intergenic transcription and developmental remodeling of chromatin subdomains in the human beta-globin locus. , 2000, Molecular cell.

[11]  D. Hogness,et al.  Regulation and products of the Ubx domain of the bithorax complex. , 1985, Cold Spring Harbor symposia on quantitative biology.

[12]  M. Bienz,et al.  Silencers in abdominal‐B, a homeotic Drosophila gene. , 1993, The EMBO journal.

[13]  E. Lewis,et al.  The molecular genetics of the bithorax complex of Drosophila: cis‐regulation in the Abdominal‐B domain. , 1990, The EMBO journal.

[14]  F. Karch,et al.  abdA expression in Drosophila embryos. , 1990, Genes & development.

[15]  P. Schedl,et al.  Chromatin domain boundaries in the Bithorax complex , 1998, Cellular and Molecular Life Sciences CMLS.

[16]  D. Hogness,et al.  Novel transcripts from the Ultrabithorax domain of the bithorax complex. , 1987, Genes & development.

[17]  F. Karch,et al.  Mcp and Fab-7: molecular analysis of putative boundaries of cis-regulatory domains in the bithorax complex of Drosophila melanogaster. , 1994, Nucleic acids research.

[18]  R. Lyle,et al.  The imprinted antisense RNA at the Igf2r locus overlaps but does not imprint Mas1 , 2000, Nature Genetics.

[19]  J. T. Kadonaga,et al.  Exploring the transcription-chromatin interface. , 2000, Genes & development.

[20]  P. Schedl,et al.  Fab-7 functions as a chromatin domain boundary to ensure proper segment specification by the Drosophila bithorax complex. , 1996, Genes & development.

[21]  E. Lewis,et al.  The abdominal region of the bithorax complex , 1985, Cell.

[22]  M. Levine,et al.  The Fab-7 element of the bithorax complex attenuates enhancer-promoter interactions in the Drosophila embryo. , 1996, Genes & development.

[23]  A. Mccarthy.  Development , 1996, Current Opinion in Neurobiology.

[24]  T. Moore,et al.  Multiple imprinted sense and antisense transcripts, differential methylation and tandem repeats in a putative imprinting control region upstream of mouse Igf2. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[25]  A. Lloyd,et al.  Molecular definition of the morphogenetic and regulatory functions and the cis-regulatory elements of the Drosophila Abd-B homeotic gene. , 1991, Development.

[26]  E. Lewis,et al.  Characterization of the intergenic RNA profile at abdominal-A and Abdominal-B in the Drosophila bithorax complex , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[27]  R Ohba,et al.  A novel histone acetyltransferase is an integral subunit of elongating RNA polymerase II holoenzyme. , 1999, Molecular cell.

[28]  E. Lewis.  A gene complex controlling segmentation in Drosophila , 1978, Nature.

[29]  P. Schedl,et al.  A Polycomb and GAGA dependent silencer adjoins the Fab-7 boundary in the Drosophila bithorax complex. , 1997, Genetics.

[30]  J. Hirsh,et al.  The zfh-2 gene product is a potential regulator of neuron-specific dopa decarboxylase gene expression in Drosophila. , 1992, Developmental biology.

[31]  R. A. Drewell,et al.  Novel conserved elements upstream of the H19 gene are transcribed and act as mesodermal enhancers. , 2002, Development.

[32]  M. Levine,et al.  Spatially regulated expression of homeotic genes in Drosophila. , 1985, Science.

[33]  T. Parnell,et al.  Differences in insulator properties revealed by enhancer blocking assays on episomes , 2000, The EMBO journal.

[34]  V. Pirrotta,et al.  The mcp element from the Drosophila melanogaster bithorax complex mediates long-distance regulatory interactions. , 1999, Genetics.

[35]  E. Lewis,et al.  Complete sequence of the bithorax complex of Drosophila. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[36]  M. Levine,et al.  Gap genes define the limits of antennapedia and bithorax gene expression during early development in Drosophila. , 1988, The EMBO journal.

[37]  S. Poux,et al.  Structure of a Polycomb Response Element and In Vitro Binding of Polycomb Group Complexes Containing GAGA Factor , 2000, Molecular and Cellular Biology.

[38]  F. Karch,et al.  In situ dissection of the Fab-7 region of the bithorax complex into a chromatin domain boundary and a Polycomb-response element. , 1997, Development.

[39]  E. Sánchez-Herrero.  Control of the expression of the bithorax complex genes abdominal-A and abdominal-B by cis-regulatory regions in Drosophila embryos. , 1991, Development.

[40]  W. Bender,et al.  Enhancer point mutation results in a homeotic transformation in Drosophila. , 1994, Science.

[41]  P. Ingham,et al.  The correct activation of Antennapedia and bithorax complex genes requires the fushi tarazu gene , 1986, Nature.

[42]  M. Levine,et al.  Different core promoters possess distinct regulatory activities in the Drosophila embryo. , 1998, Genes & development.

[43]  M. Levine,et al.  Regulation of even‐skipped stripe 2 in the Drosophila embryo. , 1992, The EMBO journal.

[44]  E. Sánchez-Herrero,et al.  Regulation of the infraabdominal regions of the bithorax complex of Drosophila by gap genes. , 1995, Development.

[45]  W. Bender,et al.  Transcription activates repressed domains in the Drosophila bithorax complex. , 2002, Development.

[46]  R. Paro,et al.  Transcription through Intergenic Chromosomal Memory Elements of the Drosophila Bithorax Complex Correlates with an Epigenetic Switch , 2002, Molecular and Cellular Biology.

[47]  C. Burks,et al.  Characterization of the transvection mediating region of the abdominal-B locus in Drosophila. , 1999, Development.