Visualization of trans-homolog enhancer-promoter interactions at the Abd-B Hox locus in the Drosophila embryo.
The Hox gene Abdominal-B (Abd-B) controls the morphogenesis of posterior abdominal segments in Drosophila. Expression is regulated by a series of 3' enhancers that are themselves transcribed. RNA FISH was used to visualize nascent transcripts associated with coding and noncoding regions of Abd-B in developing embryos. Confocal imaging suggests that distal enhancers often loop to the Abd-B promoter region. Surprisingly, enhancers located on one chromosome frequently associate with the Abd-B transcription unit located on the other homolog. These trans-homolog interactions can be interpreted as the direct visualization of a genetic phenomenon known as transvection, whereby certain mutations in Abd-B can be rescued in trans by the other copy of the gene. A 10 kb sequence in the 3' flanking region mediates tight pairing of Abd-B alleles, thereby facilitating trans looping of distal enhancers. Such trans-homolog interactions might be a common mechanism of gene regulation in higher metazoans.
Ronshaugen
Matthew
M
Department of Molecular Cell Biology, Division of Genetics, Center for Integrative Genomics, University of California, Berkeley, Berkeley, CA 94720, USA. mronshau@uclink.berkeley.edu
Levine
Mike
M
D000483:Alleles; D000818:Animals; D004247:DNA / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics*; D004331:Drosophila melanogaster / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D018398:Homeodomain Proteins / Q000235:genetics*; D006720:Homozygote; D007091:Image Processing, Computer-Assisted; D017404:In Situ Hybridization, Fluorescence; D018613:Microscopy, Confocal; D008954:Models, Biological; D008957:Models, Genetic; D009154:Mutation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012313:RNA / Q000737:chemistry; D012333:RNA, Messenger / Q000378:metabolism; D014158:Transcription, Genetic
C062393:Abd-B proteins, Drosophila; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D012333:RNA, Messenger; D012313:RNA; D004247:DNA