Drosophila Single-minded Represses Gene Transcription by Activating the Expression of Repressive Factors

摘要

TheDrosophilasingle-mindedgenecontrolsCNSmidlinecelldevelopmentbybothactivatingmidlinegeneexpressionandrepressinglateralCNSgeneexpressioninthemidlinecells.ThemechanismbywhichSingle-mindedrepressestranscriptionwasexaminedusingtheventralnervoussystemdefectivegeneasatargetgene.Transgenic-lacZanalysisofconstructscontainingfragmentsoftheventralnervoussystemdefectiveregulatoryregionidentifiedsequencesrequiredforlateralCNStranscriptionandmidlinerepression.EliminationofSingle-minded:Tangobindingsiteswithintheventralnervoussystemdefectivegenedidnotaffectmidlinerepression.MutantsofSingle-mindedthatremovedtheDNAbindingandtranscriptionalactivationregionsabolishedventralnervoussystemdefectiverepression,aswellastranscriptionalactivationofothergenes.ThereplacementoftheSingle-mindedtranscriptionalactivationregionwithaheterologousVP16transcriptionalactivationregionrestoredtheabilityofSingle-mindedtobothactivateandrepresstranscription.TheseresultsindicatethatSingle-mindedindirectlyrepressestranscriptionbyactivatingtheexpressionofrepressivefactors.Single-mindedprovidesamodelsystemforhowregulatoryproteinsthatactonlyastranscriptionalactivatorscancontrollineage-specifictranscriptioninbothpositiveandnegativemodes.