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Gene Review

Scr  -  Sex combs reduced

Drosophila melanogaster

Synonyms: BG:DS07876.2, CG1030, DmScr, Dmel\CG1030, Homeotic protein Sex combs reduced, ...
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Disease relevance of Scr

  • 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 [1].
  • After head involution occurs, Scr protein is also expressed in the ganglion corresponding to parasegment 2 of the ventral nervous system [2].

High impact information on Scr


Biological context of Scr

  • We have identified genes that limit where the homeotic gene Sex combs reduced (Scr) can affect cell fates in the Drosophila embryo [6].
  • Third, we analyzed a set of Scr-lacZ enhancer tester constructs [7].
  • Taken together, our data suggests that Scr gene expression is differentially regulated both temporally and spatially in a manner that is sensitive to the structure of the locus [8].
  • 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 [1].
  • Additionally, we have found that the spatial pattern of Scr gene expression in imaginal tissues involved in the development of the adult thorax is governed in part by synapsis of homologous chromosomes in this region of the ANT-C [8].

Anatomical context of Scr


Associations of Scr with chemical compounds

  • The repressor activity of one fragment, normally located in Scr Intron 2, is increased when it is able to homologously pair, a property consistent with genetic data suggesting that Scr exhibits transvection [12].
  • Scr encodes a 417-amino-acid DNA-binding protein with sequence similarity to the mouse homologues, HOXA5, B5 and C5 [13].

Physical interactions of Scr

  • We find that in the absence of the bithorax complex (BX-C) genes there is Scr expression in the epidermis of the posterior compartments of the thoracic and abdominal parasegments [14].
  • In the case of the Drosophila Antennapedia complex, the T1 enhancer bypasses the neighboring ftz gene and interacts with the distant Scr promoter to activate expression in posterior head segments [15].
  • A DROSOPHILA: homologue of the regulatory subunit (B'/PR61) of serine-threonine protein phosphatase 2A (dPP2A,B') specifically interacted with the SCR homeodomain [16].

Regulatory relationships of Scr

  • In the abdominal cuticle Scr is prevented from inducing prothoracic structures by the three bithorax complex (BX-C) homeotic genes [6].
  • Tribolium pb therefore positively regulates distal Scr expression, a role that it has in common with Drosophila pb [17].
  • CONCLUSION: These results provide strong evidence that the Scr gene expression is influenced by direct interaction between DSP1 and two Scr regulation elements [18].
  • In the epidermis, Antp has been shown to negatively regulate Scr, but it positively regulates Scr in the visceral mesoderm [19].

Other interactions of Scr

  • Setting limits on homeotic gene function: restraint of Sex combs reduced activity by teashirt and other homeotic genes [6].
  • We propose the existence of a secondary wave of Scr activation, which takes place during germ band retraction, is triggered by en and requires Antp expression [14].
  • The Drosophila proboscis is specified by two Hox genes, proboscipedia and Sex combs reduced, via repression of leg and antennal appendage genes [20].
  • Interestingly, while previous studies have concluded that ectopic expression of the homeotic genes Dfd, Scr and Antp has no effect on the segmental identity of the abdominal segments, our results demonstrate that this is not true [21].
  • Imaginal discs from these paternally rescued embryos may show discrete patches of expression of Ubx and Scr in inappropriate locations [22].


  1. Transvection and silencing of the Scr homeotic gene of Drosophila melanogaster. Southworth, J.W., Kennison, J.A. Genetics (2002) [Pubmed]
  2. The expression and regulation of Sex combs reduced protein in Drosophila embryos. Riley, P.D., Carroll, S.B., Scott, M.P. Genes Dev. (1987) [Pubmed]
  3. The developmental effect of overexpressing a Ubx product in Drosophila embryos is dependent on its interactions with other homeotic products. González-Reyes, A., Morata, G. Cell (1990) [Pubmed]
  4. The control of trunk Hox specificity and activity by Extradenticle. Ryoo, H.D., Mann, R.S. Genes Dev. (1999) [Pubmed]
  5. A novel boundary element may facilitate independent gene regulation in the Antennapedia complex of Drosophila. Belozerov, V.E., Majumder, P., Shen, P., Cai, H.N. EMBO J. (2003) [Pubmed]
  6. Setting limits on homeotic gene function: restraint of Sex combs reduced activity by teashirt and other homeotic genes. Andrew, D.J., Horner, M.A., Petitt, M.G., Smolik, S.M., Scott, M.P. EMBO J. (1994) [Pubmed]
  7. Genetic analysis of embryonic cis-acting regulatory elements of the Drosophila homeotic gene sex combs reduced. Gorman, M.J., Kaufman, T.C. Genetics (1995) [Pubmed]
  8. The homeotic gene Sex combs reduced of Drosophila melanogaster is differentially regulated in the embryonic and imaginal stages of development. Pattatucci, A.M., Kaufman, T.C. Genetics (1991) [Pubmed]
  9. Regulation and function of Scr, exd, and hth in the Drosophila salivary gland. Henderson, K.D., Andrew, D.J. Dev. Biol. (2000) [Pubmed]
  10. Expression of the Sex combs reduced protein in Drosophila larvae. Glicksman, M.A., Brower, D.L. Dev. Biol. (1988) [Pubmed]
  11. Genetic characterization of the role of the two HOX proteins, Proboscipedia and Sex Combs Reduced, in determination of adult antennal, tarsal, maxillary palp and proboscis identities in Drosophila melanogaster. Percival-Smith, A., Weber, J., Gilfoyle, E., Wilson, P. Development (1997) [Pubmed]
  12. Identification of Polycomb and trithorax group responsive elements in the regulatory region of the Drosophila homeotic gene Sex combs reduced. Gindhart, J.G., Kaufman, T.C. Genetics (1995) [Pubmed]
  13. The Sex combs reduced gene of Drosophila melanogaster has multiple transcripts. Andrew, D.J. Gene (1995) [Pubmed]
  14. Normal and ectopic domains of the homeotic gene Sex combs reduced of Drosophila. Pelaz, S., Urquía, N., Morata, G. Development (1993) [Pubmed]
  15. Long-range enhancer-promoter interactions in the Scr-Antp interval of the Drosophila Antennapedia complex. Calhoun, V.C., Levine, M. Proc. Natl. Acad. Sci. U.S.A. (2003) [Pubmed]
  16. Phosphorylation status of the SCR homeodomain determines its functional activity: essential role for protein phosphatase 2A,B'. Berry, M., Gehring, W. EMBO J. (2000) [Pubmed]
  17. Proboscipedia represses distal signaling in the embryonic gnathal limb fields of Tribolium castaneum. DeCamillis, M., ffrench-Constant, R. Dev. Genes Evol. (2003) [Pubmed]
  18. DSP1, a Drosophila HMG protein, is involved in spatiotemporal expression of the homoeotic gene Sex combs reduced. Rappailles, A., Decoville, M., Locker, D. Biol. Cell (2005) [Pubmed]
  19. Expression and function of the homoeotic genes Antennapedia and Sex combs reduced in the embryonic midgut of Drosophila. Reuter, R., Scott, M.P. Development (1990) [Pubmed]
  20. The Drosophila proboscis is specified by two Hox genes, proboscipedia and Sex combs reduced, via repression of leg and antennal appendage genes. Abzhanov, A., Holtzman, S., Kaufman, T.C. Development (2001) [Pubmed]
  21. Homeotic genes have specific functional roles in the establishment of the Drosophila embryonic peripheral nervous system. Heuer, J.G., Kaufman, T.C. Development (1992) [Pubmed]
  22. Persistent ectopic expression of Drosophila homeotic genes resulting from maternal deficiency of the extra sex combs gene product. Glicksman, M.A., Brower, D.L. Dev. Biol. (1990) [Pubmed]
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