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Unformatted text preview: Proc. Natl.Acad. Sci. USA Vol.86,pp.8447-8451,November 1989 Evolution Vectorial expansion oftheinvolucringene and therelatedness of thehominoids PHILIPPE DJLAN AND HOWARD GREEN DepartmentofCellularandMolecularPhysiology,Harvard MedicalSchool,25ShattuckStreet,Boston,MA 02115 ContributedbyHoward Green,July17, 1989 ABSTRACT Inhigherprimates,thecodingregionofthe geneforinvolucrin,anepidermalprotein,ismostlycomposed of a recently generated (modern) segment of repeats of a sequenceof10codons.Whiletherestofthecodingregionhas evolvedonlybynucleotidesubstitutions,themodern segment hasevolvedbysuccessiveadditionofrepeats.Thisprocesshas nottakenplacerandomly;instead,theexpansionofthemodern segment hasbeen progressivefrom 3'to5'end,thusadding vectoriallyregionsthathavebeendefinedasearly,middle,and late.The relatedness ofthehuman, chimpanzee, and gorilla may beanalyzedwithgreatestsensitivityby comparing their middleregions.Thechimpanzeeinvolucringeneismore closely relatedtothatofthegorillathantothatofthehuman. Involucrin isapolypeptide substrateofkeratinocyte trans- glutaminase(1,2).Duringterminaldifferentiationofthecell, theenzymeisactivatedandinvolucrinbecomescross-linked tootherproteins,forminganinsolublecellenvelope. The nucleotidesequence oftheinvolucringene isknown forthehuman (3),gorilla(4),orangutan(5),andowlmonkey (6).Thecodingregionofthegenecontains amodem segment of repeats. This segment was generatedwithin the higher primate lineage in stages that could be defined as early, middle, and late. The early region was completed in a common ancestor of all anthropoid primates, since it is presentinspeciesaswidelyseparatedasthehuman andthe owl monkey (6).The middleregionofthehominoids devel- oped afterdivergenceoftheirlineagefrom thatoftheowl monkey, since the involucrin gene of the latter does not containacorrespondingmiddleregion.The lateregionmust have been generated afterthe divergence ofthe hominoid speciesfromeachother,sinceitisuniqueineachhominoid sofarexamined(3-5). We now reportthenucleotidesequence oftheinvolucrin geneofthechimpanzee(Pan)*andexamine therelatedness ofthesegmentofrepeatsinthisgenetothatofthehumanand gorilla.Relatedness isbased on two criteria: similarityof repeatpatternandcoincidenceofmarkernucleotides.Since therepeatsofthemodem segment arenearlyidenticaltoa consensus sequence, a non-consensus nucleotide marks a repeatandmaythereforebeusedtoestablishthattworepeats haveacommon origin. MATERIALS AND METHODS Vaginal biopsies were performed at the Yerkes Primate Center (Atlanta) on a pygmy chimpanzee (Laura) and a common chimpanzee (Garbo) and provided to R. H. Rice (Harvard School of Public Health), who prepared kerati- nocytecultures,asdescribedearlier(7,8).A restrictionmap was derivedfrom theirDNA (5)....
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