title: Regulation of expression of venom toxins: silencing of prothrombin activator trocarin D by AG-rich motifs.
abstract: Trocarin D (TroD), a venom prothrombin activator from Tropidechis carinatus, shares similar structure and function with blood coagulation factor Xa [Tropidechis carinatus FX (TrFX) a]. Their distinct physiologic roles are due to their distinct expression patterns. The genes of TroD and TrFX are highly similar, except for promoter and intron 1, indicating that TroD has probably evolved by duplication of FX, the plasma counterpart. The promoter insertion in TroD accounts for the elevated but not venom gland-specific expression. Here we examined the roles of 3 insertions and 2 deletions in intron 1 of TroD in the regulation of expression using luciferase as a reporter. By systematic deletions, we showed that a 209 bp region within the second insertion silences expression in mammalian and unmilked venom gland cells. Through bioinformatics analysis, we identified 5 AG-rich motifs in this region. All except the 5th motif are important for silencing function. YY1, Sp3 and HMGB2 were identified to bind these AG-rich motifs and silence gene expression in mammalian cells. Similar AG-rich motif clusters are also found in other toxin genes but not in their physiologic counterparts. Thus, AG-rich motifs contribute to regulation of expression of TroD, and probably other toxin genes.-Han, S. X., Kwong, S., Ge, R., Kolatkar, P. R., Woods, A. E., Blanchet, G., Kini, R. M. Regulation of expression of venom toxins: silencing of prothrombin activator trocarin D by AG-rich motifs.
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore;
authors.forename: Summer Xia
authors.initials: SX
authors.lastname: Han
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore;
authors.forename: Shiyang
authors.initials: S
authors.lastname: Kwong
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore;
authors.forename: Ruowen
authors.initials: R
authors.lastname: Ge
authors.affiliation: Qatar Biomedical Research Institute, Hamad Bin Khalifa University, Qatar Foundation for Education, Science, and Community Development, Doha, Qatar; and.
authors.forename: Prasanna R
authors.initials: PR
authors.lastname: Kolatkar
authors.affiliation: School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, South Australia, Australia.
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Woods
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore;
authors.forename: Guillaume
authors.initials: G
authors.lastname: Blanchet
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore; dbskinim@nus.edu.sg.
authors.forename: R Manjunatha
authors.initials: RM
authors.lastname: Kini
mesh_terms: D000818:Animals; D001483:Base Sequence; D004247:DNA; D004546:Elapid Venoms / Q000737:chemistry*; D017815:Elapidae / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D057809:HEK293 Cells; D056945:Hep G2 Cells; D006801:Humans; D011516:Prothrombin / Q000037:antagonists & inhibitors*; D034622:RNA Interference; D034741:RNA, Small Interfering
chemical_list: D004546:Elapid Venoms; D034741:RNA, Small Interfering; C120393:trocarin; D011516:Prothrombin; D004247:DNA
keywords: purine repeat sequences; toxin gene evolution; transcriptional repression