Histones ke ... Karolo ea histori ea DNA

Nucleic acid DNA, e kenang mokokotlong oa lisele tsa eukaryotic, e khotsofatsoa ka lebaka la mehaho e khethehileng. Ka cytology ba na le lebitso le khethehileng - histones. Tsena ke li-peptide tse bontšang lik'hemik'hale tsa motheo tsa motheo. Sebopeho sa bona le mesebetsi e entsoeng ka seleng li tla tšohloa sehloohong sena.

Kamoo DNA e hlophisitsoeng kateng mokokotlong

E le hore u "pepese" ketane e telele ea polynucleotide ea DNA ka microcosm ea nucleus ea sele, ho na le "lihlahisoa" tsa pele - liprotheine-histones. Li na le li-stranded stranded deoxyribonucleic acid. Sebaka se joalo, se karyoplasm, se bitsoa nucleosome. Liphuputso tsa likokoana-hloko li thehile hore histone protein e hlophisitsoe ka mokhoa o itseng oa phetoho e 'maloa: histone H1 / H5, H2A, H2B, H3, H4. Peptide ea pele lethathamong lena hangata e bitsoa linker, tse ling kaofela ke li-crustaceans. Ke liprotheine-historiones tse etsang nucleosome.

Lintho tse ikhethang tsa sebopeho sa li-peptide tsa nucleosome

K'hemik'hale ea lik'hemik'hale e thehiloe 'nete ea likhahla tse feteletseng tsa li-molecule tsa limolek'hule tsa amino acid tse kang lysine le arginine. Ntho ea pele e ke ke ea senyeha, 'me e' ngoe e nkeloa sebaka hape 'me e teng hoo e ka bang li-peptide tsohle. Li-proteine-histones li bokella lits'enyehelo tse ngata tsa lichelete tsa amino acid. Ba fokotsa linyeoe tse mpe tsa li-ani- _{4 tsa} ani- ₄ tse etsang DNA. Tšobotsi e 'ngoe ea sebopeho sa liprotheine tsena ke hore e tšoana le libōpong tsa' muso oa semela, liphoofolo le li-mushroom.

Kaha li-histones ke liprotheine tsa motsoako, li ka ba teng letsoho litulong tse hlahang karyoplasm. Ka mohlala, ntho ea bohlokoa ka ho fetisisa bakeng sa ts'ebetso ea ho ngolisa ke peptide H1, protheine ea histone e tšoereng li-nucleosomes tse karolong ea chromatin e le mokokotlo o laetsoeng. Hape, tabeng ea tšenyo ea DNA loci, li bitsoang limolek'hule tse sa tšoaneng tsa li-peptide tsa mantlha li kenya letsoho ho lokisa liwebsaete tsena.

Pela peptides

Ba khetholla sebopeho sa nucleosome, e nang le mefuta e mene ea limolek'hule e bitsoang H2A, H2B le H3 le H4. Li-nucleosomes ho na le limolek'hule tse peli tsa mofuta o mong le o mong, mohaho ona o bitsoa octamer. Molek'hule ea deoxyribonucleic le liprotheine tsa mantlha li theha lilekane tsa hydrophobic, hydrogen le covalent pakeng tsa bona. Li-proteine-histones ke tsona tse ka sehloohong tsa nucleosome. Li boetse li na le mehatla ea NC e sa hlahisoang. Likarolo tsena li na le lihlahisoa tse 15-30 tsa amino acid le ho kenya letsoho liketsong tsa epigenetic tse laolang polelo ea liphatsa tsa lefutso. Li-histone tse ka sehloohong tsa karolo ea bohareng ba nucleosome li na le litekanyo tse nyenyane tsa limolek'hule; likarolong tsa tsona, ho fapana le likarolo tsa mohatla, ho na le lihlekehleke tsa hydrophobic protheine monomers: valine, proline, lezine, methionine.

Phuputso ea morao-rao ea saense lefapheng la phekolo ea likokoana-hloko e entse hore ho be le khopolo ea khopolo ea histone. Ho fapana le liphatsa tsa lefutso, tse leng hohle bakeng sa mefuta eohle ea bophelo ba lik'hamera Lefatšeng, molaetsa oa histone o fapane. Lentsoe lena le bolela ho fetoloa ha mohatla oa likarolo tsa peptide ka lebaka la liketso tsa acetylation, methylation, phosphorylation. Lik'hemik'hale tsena tsohle tse ka holimo li etsahala ka boteng ba mekhoa ea multienzyme. Ka lebaka la mekhoa e joalo ea likokoana-hloko e fetolang li-histone tsa motheo, polelo ea ho lokisoa ha liphatsa tsa lefutso tse laolang liphello tsa intranuclear tse akarelletsang DNA: phetolo, phetolelo, ho iphetola ho etsahala. Chromatin ka boeona ka tlas'a tšusumetsano ea liphetoho tsa khopolo ea histone e fetoleloa hape, ke hore, e fetola liphutheloana tsa eona nucleosome (ea e fokotsa kapa, ka lehlakoreng le leng, e lokolla).

Linker protheine

Histone H1, e leng ka chromatin, e kopantsoeng le karolong e ka ntle ea nucleosome 'me e boloka eona e kholo-holo ea deoxyribonucleic acid. Ho lokisoa ha eona ho etsahala sebakeng sa tetramer e nang le limolek'hule tse peli tsa peptide H3 le limolek'hule tse peli tsa H4. Ho baemeli ba sehlopha sa linonyana le sehlopha sa lihahabi li-erythrocyte, e 'ngoe ea protheine ea H5 e fumanoa ho e-na le ea historione H1.

Peptide ea H1 e na le sebaka sa HMJB, sebaka sa moralo sa lihlahisoa tse ka bang 80 tsa amino acid. E batla e tšoana le liphoofolo tse ngata, ho kenyelletsa limela, liphoofolo le batho. Sebaka sena sa marang-rang ha se khone ho fetoloa mme se ikemetse. Peptide H1 e na le mefuta e 'meli ea phetoho ea sebaka: e kenngoe ka mokhoa oa lefats'e mme o sebelisoa - ka mokhoa o phahameng. Ho qetella ho etsahala ha ho amana ha sebaka sa C-terminone ea histone le libaka tsa DNA tse tlamang li robehile. Peptide ea linker e ikakhela ka setotsoana ho ngola boitsebiso bo tsoang ho liphatsa tsa lefutso ho molek'hule ea mRNA, litšebelisanong tsa DNA ho ipheta-pheta, hammoho le ho lokisoa ha loci e senyehileng. Ena ke karolo ea li-histone tsa DNA.

Liprotheine li theha octamer joang

Ho fapana le peptide H1, mefuta e meng ea histones, e bitsoang li-crustaceans, e khetholloa ka polasetiki e lekaneng le mefuta e sa tšoaneng. Ka mohlala, H2A e na le palo e kholo ka ho fetisisa ea liphetoho: H2AZH2AX MACROH2A. Li fapana ka bobona:

• C-terminal amino acid e setseng.
• Sebaka sa genome.

Ka mohlala, histone H2ABbd e fapaneng e amana le chromatin, ho DNA eo ho eona ho ngotsoeng phetolelo. Peptide ea MACROH2A e fumaneha ka li-chromosome tsa interphase. Liphuputso tsa Cytolo li bontšitse hore histone H4 ha e na mefuta e fapa-fapaneng, empa e khona ho theha palo e kholo ea lilekane tse kopantsoeng le liprotheine tse ling tse kenang ka octamer ea nucleosome. Ka hona, bo-rasaense ba lumela hore histones ke sehlopha sa liprotheine tse ikhethang tse kenyang chromatin ea mefuta eohle ea li-cellular.

Tlhahisoleseding e mabapi le histones ea genome e bolokiloe joang

Ho ka pheha khang ea hore li-crustal, linker le histones tse sa tšoaneng li ngotsoe ka lihlopha tsa liphatsa tsa lefutso tse hlalositsoeng ka karolo ea mahlakore a sele ea bophelo. Ka mohlala, bakeng sa motho, sehlopha sa lefutso se nang le lefa, se bitsoang HIST1, se na le liphatsa tsa lefutso tse 35 tse fumanehang ka har'a li-chromosome tse peli tsa somatic. Sehlopha sa HIST2 se na le liphatsa tsa lefutso tse tšeletseng tse koetlisang historione 'me li fumaneha ho sehlopha sa pele sa chromosome. E boetse e na le locus HIST3, e akarelletsang liphatsa tsa lefutso tse tharo. Lekhalong la leshome la metso e 'meli, ho na le liphatsa tse ling tse lekanang tsa lefutso tsa histone H4. Ho thahasellisang ke hore liphatsa tsa lefutso tsa liprotheine tse phoroselang ha li na li-introns, 'me liphatsa tsa lefutso tsa histones tse fapaneng, ho fapana le tsona, li na le tsona' me li hasane ho pholletsa le genome.

Ho akaretsa, re ne re kholisehile hore histones ke liprotheine tse kenyelletsang ho beha DNA helix mokokotlong, hammoho le ho laola, ho lokisoa le mekhoa ea ho ngolisa e hlahang ho eona.