Histones - nws ... Lub luag hauj lwm ntawm histones nyob rau hauv lub DNA

Nucleic acid DNA muaj nyob rau hauv lub nucleus ntawm eukaryotic hlwb, compact fej ua tsaug rau tshwj xeeb lug. Nyob rau hauv cytology lawv hnav ib tug tshwj xeeb lub npe - histones. Nws yog ib tug peptide uas qhia qhov yooj yim tshuaj zog. Lawv cov qauv thiab kev khiav dej num ua nyob rau hauv lub cell, yuav tsum tau tham nyob rau hauv no tsab xov xwm.

DNA yog lub koom haum nyob rau hauv lub nucleus

Nyob rau hauv thiaj li yuav "nyem" ntev polynucleotide saw ntawm DNA nyob rau hauv microspace cell nucleus nyob rau ntawd yog peculiar "kauj" - cov nqaijrog, histones. Lawv muab ob npaug rau-tso tseg xov yog lub qhov txhab deoxyribonucleic acid. Qhov no qauv, nyob rau hauv karyoplasm yog hu ua ib tug nucleosome. Biochemical kev tshawb fawb qhia tau hais tias histone protein quas ob peb hloov: histone H1 / H5, H2A, H2B, H3, H4. Tus thawj peptide ntawm daim ntawv no yog hu ua ib tug Linker, lwm nyuj. Cov histone cov nqaijrog tsim nucleosome.

Nta ntawm cov qauv ntawm cov nucleosome peptides

Tshuaj tsom xam tsim lub fact ntawm ntau cov ntsiab lus nyob rau hauv cov tub ntxhais histone molecules ntawm amino acids xws li lysine thiab arginine. Tus thawj yog qhov tseem ceeb thiab lwm yam cov interchangeable thiab yog tam sim no nyob rau hauv txhua peptides. Histone cov nqaijrog noog excess zoo xwb nyob rau hauv cov amino acid residues. Lawv neutralize qhov tsis zoo nqi ntawm tag nrho cov PO ₄ ^3- anions, muaj nyob rau hauv cov DNA. Lwm feature ntawm cov qauv ntawm cov nqaijrog lus dag nyob rau hauv lub fact tias nws yog yuav luag zoo tib yam nyob rau hauv cov kab mob teej tug mus rau hauv lub nceeg vaj ntawm cov nroj tsuag, tsiaj txhu thiab fungi.

Txij li thaum histones - cov nqaijrog yog cov tub ntxhais, lawv yog vim nws cov qauv, yuav koom nyob rau hauv cov txheej txheem tshwm sim nyob rau karyoplasm. Piv txwv li, qhov tseem ceeb rau lub transcription txheej txheem H1 peptide - histone protein ceev nucleosomes yog ib feem ntawm chromatin nyob rau hauv ib yaam, compact tub ntxhais. Tsis tas li ntawd, nyob rau hauv cov ntaub ntawv ntawm kev puas tsuaj DNA loci, thiaj li hu ua tub ntxhais peptide variant molecules yog muab kev koom tes nyob rau hauv lub kho ntawm cov qhov chaw.

cov tub ntxhais peptide

Lawv txhais cov qauv ntawm cov nucleosome, uas muaj plaub hom molecules hu ua H2A, H2B thiab H3 thiab H4. Lub nucleosomes yog ob tug ntawm txhua hom qauv, xws li ib tug qauv yog hu ua octamer. Cov qauv ntawm deoxyribonucleic tub ntxhais cov nqaijrog thiab daim ntawv nruab nrab ntawm lawv hydrophobic, hydrogen thiab covalent bonds. Cov nqaijrog, histones yog nyob rau tub ntxhais ntawm lub nucleosome. lawv kuj muaj unstructured NC-tails. Tej yam muaj xws li 15-30 amino acid residues thiab yog muab kev koom tes nyob rau hauv lub epigenetic dab uas tswj noob qhia. Core histones central feem nucleosomes muaj me me molecular luj, nyob rau hauv lawv cov chaw, tsis zoo li tus Tsov tus tw feem islets muaj hydrophobic monomers protein valine, proline, Lezina methionine.

Tsis ntev los no kev tshawb fawb nyob rau hauv lub teb ntawm biochemistry tau coj mus rau lub hypothesis ntawm lub histone code. Nyob rau hauv sib piv rau lub caj code yog universal rau tag nrho cov ntaub ntawv ntawm cov cellular lub neej nyob rau lub ntiaj teb, lub histone code yog nce mus nce los. Qhov no lub sij hawm txhais tau tias modifying tus Tsov tus tw feem ntawm lub peptides uas ua los ntawm cov acetylation cov tshuaj tiv thaiv, methylation, ntsev. Tag nrho cov tshuaj dab tshwm sim nyob rau hauv lub xub ntiag ntawm multienzyme ceg. Vim xws biochemical dab, cov modifying tub ntxhais histones, thiab hloov yuav siv sij hawm qhov chaw qhia ntawm noob uas tswj intranuclear tshua uas DNA: kho, transcription, replication. Nws tus kheej nyob rau hauv tus ntawm lub chromatin histone code hloov undergoes kho, piv txwv li kev hloov nws ntim rau hauv lub nucleosome (cov ntsaws ruaj ruaj nws los yog, nyob rau hauv tsis tooj, loosens).

Linker protein

Histone H1 yog nyob rau hauv chromatin, yog kev cob cog rua rau lub txheej ntawm lub nucleosome thiab khaws thereon supercoil deoxyribonucleic acid. Nws fixation tshwm sim nyob rau qhov chaw tetramer muaj ob peptide molecules H3 thiab H4 ob molecules. Cov neeg sawv cev ntawm cov chav kawm ntawv thiab cov chav kawm ntawm cov noog cov tsiaj reptiles nyob rau hauv cov ntshav liab tsis histone H1 Linker protein pom lwm tus H5.

H1 peptide comprises HMJB sau - ib tug yam ntxwv feem, nrog kwv yees li 80 amino acid residues. Nws yog suab tib yam nyob rau hauv feem ntau cov kab mob, nrog rau cov nroj tsuag, tsiaj txhu thiab tib neeg. Qhov no sau tsis yog kev kawm mus rau kev hloov kho thiab yog conservative. Peptide N1 muaj ob hom ntawm spatial configurations: ib tug collapsed globule thiab unfolded - nyob rau hauv tertiary daim ntawv. Cov yav tas muaj tshwm sim thaum kev sib txuas lus tsis C-davhlau ya nyob twg cheeb tsam ntawm lub histone mus rau lub DNA-losis tswvyim dabtsi thawj. Lub Linker peptide yog kev koom tes nyob rau hauv luam ntawm cov ntaub ntawv los ntawm noob rau mRNA molecule, ib tug self-doubling DNA dab, raws li tau zoo raws li nyob rau hauv lub kho ntawm puas nws loci. Qhov no yog qhov lom luag hauj lwm ntawm histones nyob rau hauv lub DNA.

Raws li cov proteins uas tsim octamer

Tsis zoo li peptide H1, lwm yam histones hu ua nyuj, yus muaj los ntawm txaus ductility tsim tau ib cov variant daim ntawv. Piv txwv li, H2A muaj lub siab tshaj plaws pes tsawg tus ntawm kev hloov kho: H2AZH2AX MACROH2A. Lawv txawv los ntawm txhua lwm yam:

• C-davhlau ya nyob twg amino acid ib theem zuj zus.
• Qhov chaw nyob rau hauv lub genome.

Piv txwv li, histone variant H2ABbd interconnected nrog chromatin nyob rau hauv uas DNA transcription tshwm sim. MACROH2A peptide yog nyob rau hauv interphase chromosomes. Cytological kev tshawb fawb nws twb pom hais tias cov histone H4 variant cov ntaub ntawv tau raug pom tias yog, tiam sis nws muaj peev xwm tsim ib tug loj tus naj npawb ntawm covalent bonds nrog lwm cov nqaijrog teej tug mus rau lub octamer nucleosomes. Yog li, zaum ntseeg tias lub histones - ib tug tshwj xeeb cov pab pawg neeg ntawm cov nqaijrog uas tseem suab ib feem ntawm lub chromatin ntawm tag nrho cov cellular ntaub ntawv ntawm lub neej.

Yuav ua li cas cia ntaub ntawv hais txog lub histones nyob rau hauv lub genome

Nws yuav sib cav hais tias cov nyuj, thiab cov Linker histone variant encoded nyob rau hauv lub noob pawg qhia nyob rau hauv cov khoom cua theem ntawm lub cell lub neej voj voog. Piv txwv li, rau tib neeg raws roj ntsha sijhawm pab pawg neeg hu ua HIST1 nws muaj 35 noob nyob rau hauv lub thib rau lub Somatic chromosome khub. HIST2 pawg muaj rau noob encoding histones, thiab cov chromosomal qhov chaw ntawm ib tug thawj khub. Nws kuj muaj ib tug locus HIST3, muaj peb cov noob. Nyob rau hauv lub kaum ob khub yog ib tug noob encoding ib histone H4. Interestingly, cov tub ntxhais protein noob muaj introns, thiab noob ntawm variant histones, on qhov tsis tooj, muaj lawv thiab tawg ri niab mus thoob plaws hauv lub genome.

Yuav kom saib lub ntsab lug, peb pom tau hais tias cov histones - cov nqaijrog yog muab kev koom tes nyob rau hauv pw lub strands ntawm DNA nyob rau hauv lub nucleus, tab sis kuj nyob rau hauv cov txheej txheem ntawm kev cai, kho thiab transcription muab qhov chaw nyob rau hauv nws.