Transvection and Silencing of the Scr Homeotic Gene of Drosophila melanogaster

Corresponding author: James A. Kennison, Rm. 3B-331, NIH, Bethesda, MD 20892-2785., jim_kennison{at}nih.gov (E-mail)

Communicating editor: T. C. KAUFMAN

The Sex combs reduced (Scr) gene specifies the identities of the labial and first thoracic segments in Drosophila melanogaster. In imaginal cells, some Scr mutations allow cis-regulatory elements on one chromosome to stimulate expression of the promoter on the homolog, a phenomenon that was named transvection by Ed Lewis in 1954. Transvection at the Scr gene is blocked by rearrangements that disrupt pairing, but is zeste independent. Silencing of the Scr gene in the second and third thoracic segments, which requires the Polycomb group proteins, is disrupted by most chromosomal aberrations within the Scr gene. Some chromosomal aberrations completely derepress Scr even in the presence of normal levels of all Polycomb group proteins. On the basis of the pattern of chromosomal aberrations that disrupt Scr gene silencing, we propose a model in which two cis-regulatory elements interact to stabilize silencing of any promoter or cis-regulatory element physically between them. This model also explains the anomalous behavior of the Scx allele of the flanking homeotic gene, Antennapedia. This allele, which is associated with an insertion near the Antennapedia P1 promoter, inactivates the Antennapedia P1 and P2 promoters in cis and derepresses the Scr promoters both in cis and on the homologous chromosome.

This article has been cited by other articles:

				L. Sivanantharajah and A. Percival-Smith Analysis of the Sequence and Phenotype of Drosophila Sex combs reduced Alleles Reveals Potential Functions of Conserved Protein Motifs of the Sex combs reduced Protein Genetics, May 1, 2009; 182(1): 191 - 203. [Abstract] [Full Text] [PDF]

				H. Liu, J. Huang, J. Wang, S. Jiang, A. S. Bailey, D. C. Goldman, M. Welcker, V. Bedell, M. L. Slovak, B. Clurman, et al. Transvection mediated by the translocated cyclin D1 locus in mantle cell lymphoma J. Exp. Med., August 4, 2008; 205(8): 1843 - 1858. [Abstract] [Full Text] [PDF]

				D. Gohl, M. Muller, V. Pirrotta, M. Affolter, and P. Schedl Enhancer Blocking and Transvection at the Drosophila apterous Locus Genetics, January 1, 2008; 178(1): 127 - 143. [Abstract] [Full Text] [PDF]

				A. B. Coulthard, N. Nolan, J. B. Bell, and A. J. Hilliker Transvection at the vestigial Locus of Drosophila melanogaster Genetics, August 1, 2005; 170(4): 1711 - 1721. [Abstract] [Full Text] [PDF]

				L. Gutierrez, M. Zurita, J. A. Kennison, and M. Vazquez The Drosophila trithorax group gene tonalli(tna) interacts genetically with the Brahma remodeling complex and encodes an SP-RING finger protein Development, March 2, 2003; 130(2): 343 - 354. [Abstract] [Full Text] [PDF]