简介：U7smallnuclearRNA(snRNA)sequenceshavebeendescribedonlyforahandfulofanimalspeciesinthepast.Herewedescribeacomputationalsearchforfunc-tionalU7snRNAgenesthroughoutvertebratesincludingtheupstreamsequenceelementscharacteristicforsnRNAstranscribedbypolymeraseⅡ.Basedontheresultsofthissearch,wediscussthehighvariabilityofU7snRNAsinbothse-quenceandstructure,andreportonanattempttofindU7snRNAsequencesinbasaldeuterostomesandnon-drosophilidsinsectgenomesbasedonacombinationofsequence,structure,andpromoterfeatures.Duetotheextremelyshortse-quenceandthehighvariabilityinbothsequenceandstructure,nounambiguouscandidateswerefound.TheseresultscastdoubtonputativeU7homologsinevenmoredistantorganismsthatarereportedinthemostrecentreleaseoftheRfamdatabase.