I-Mitochondrial DNA (mtDNA) Indlela Yokuphindaphinda, Izinto

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HSP umgqugquzeli we-strand esindayo
I-LSP ukukhanya strand umgqugquzeli
MGME1 i-mitochondrial genome maintenance exonuclease 1
mtSSB I-mitochondrial enemicu eyodwa ye-DNA-binding protein
NCR isifunda esingabhali ikhodi
I-TAS ukulandelana okuhlobene nokuqedwa
  • I-Mitochondrial DNA (mtDNA) iyi-molecule eyi-16.6 kilobase enemicu ephindwe kabili.
  • Umucu owodwa we-DNA ye-mitochondrial inothe ngama-guanines, okuvumela ukuminyana kwe-centrifugation kumagrediyenti e-alkaline e-CsCl2 ukuhlukanisa phakathi komucu osindayo (H) kanye nolula (L).
  • I-Mitochondrial DNA (mtDNA) ihlanganisa isifunda esingenakhodi ende (NCR), esaziwa nangokuthi isifunda sokulawula.
  • Ku-NCR, umucu we-mtDNA ngamunye unomgqugquzeli wakhe wokulotshwa kwe-polycistronic: i-light strand promoter (LSP) kanye ne-heavy strand promoter (HSP) (HSP).
  • Ukwengeza, i-NCR iqukethe umsuka we-H-strand DNA replication (OH). Imvelaphi yesibili yokuphindaphinda kwe-DNA ye-L-strand (OL) itholakala ngaphandle kwe-NCR, kuqoqo le-tRNA cishe ngo-11,000 bp ngemva kwe-OH.

Isakhiwo se-mtDNA yomuntu

  • Ama-RNA ezithunywa eziyishumi nantathu (ama-mRNA; aluhlaza okotshani), ama-tRNA angamashumi amabili nambili (tRNAs; i-violet), kanye nama-RNA amabili e-ribosomal (rRNAs; ama-blue blue) wonke afakwe ikhodi ye-genome.
  • Okuphezulu kukhombisa ukukhuliswa kwesifunda esibalulekile esingafaki ikhodi (NCR).
  • Ngokungeziwe kumsuka we-H-strand wokuphindaphinda (OH) kanye nokulandelana okuhlobene nokunqanyulwa, i-NCR eyinhloko iphinde ihlanganise nomgqugquzeli we-light-strand (LSP), umgqugquzeli we-heavy-strand (HSP), amabhokisi okulandelana alondoloziwe amathathu (CSB1- 3, osawolintshi), kanye ne-HSP (TAS, ephuzi).
  • Ukuphazamiseka kokuhlanganiswa kwe-DNA okuqhubekayo ku-TAS kuphumela ekwakhekeni kwesakhiwo se-triple-stranded displacement-loop (D-loop).
  • I-7S DNA igama elinikezwe umkhiqizo omfushane wokuphindaphinda we-H owenziwe ngale ndlela.
  • Umsuka wokuphindaphinda we-L-strand we-DNA ungatholakala ku-NCR encane cishe ngamapheya ayisisekelo ayi-11,000 (bp) ngemva kwe-OH (OL).
Isakhiwo se-mtDNA yomuntu
Isakhiwo se-mtDNA Yomuntu | Umthombo: doi.org/10.1042%2FEBC20170100

Izinto zokuphindaphinda kwe-mtDNA

  • I-DNA ye-mitochondrial yezilwane ezincelisayo (mtDNA) ikopishwa amaprotheni ahlukile kulawo akopisha i-nuclear DNA, futhi amaningi alawa maprotheni afana nezici zokuphindaphinda ezitholakala kuma-bacteriophages.
  • I-DNA polymerase γ (POLγ) yi-polymerase ku-mitochondria eyenza amakhophi e-DNA. Kumaseli omuntu, i-POLγ iyi-heterotrimer eneyunithi eyodwa eyenza umsebenzi (POLγ A) kanye namayunithi amancane amabili ayisiza ukwenza umsebenzi wayo (POLγB).
  • Ukuthatha i-POLγA ne-POLγB kumagundane kubonise ukuthi kokubili kubalulekile ekukhuleni kombungu.
  • Okungenani ama-polymerase amane ngaphezulu (PrimPol, DNA polymerase θ, DNA polymerase β, kanye ne-DNA polymerase ζ) kucatshangwa ukuthi adlala indima ku-mitochondria.
  • Lawa ma-polymerase awadingeki ukuze kugcinwe i-mtDNA iphila, futhi akukho neyodwa yawo engangena esikhundleni se-POLγ.
  • Cishe, asiza ukulungisa i-mtDNA, kodwa indima eqondile yalawa ma-polymerase engeziwe ekugcineni i-mtDNA isesimweni esihle idinga ukucatshangelwa.
  • I-POLγA iyi-DNA polymerase evela emndenini A. Inesizinda se-exonuclease esingu-3′–5′ esihlola umucu we-DNA osanda kwenziwa ukuze uthole amaphutha.
  • I-POLγ iyi-DNA polymerase enembe kakhulu eyenza amaphutha angaphansi kuka-1 x 10^-6 wesikhathi.
  • Iyunithi encane ye-POLBγ iyisengezo esiza i-POLγA isebenzisane kangcono nesifanekiso se-DNA futhi ikhulise kokubili umsebenzi wayo we-catalytic kanye nesivinini sayo.
  • I-POLγ ayikwazi ukusebenzisa i-DNA enemicu ekabili njengesifanekiso, ngakho-ke kwimfoloko yokuphindaphinda ye-mitochondrial, kudingeka kube ne-DNA helicase.
  • I-DNA helicase i-TWINKLE ifana ne-T7 phage gene 4 protein. Ngesikhathi sokuphindaphinda kwe-mtDNA, i-TWINKLE ihamba phambi kwe-POLγ futhi ikhulula isifanekiso se-DNA esinemicu ekabili.
  • I-TWINKLE yenza i-hexamer futhi idinga ukwakheka kwemfoloko (isayithi yokulayisha engu-5′-DNA enomucu owodwa kanye nomsila ongu-3) omfushane ukuze ilayishe futhi iqale ukuqaqa.
  • I-Mitochondrial single-stranded DNA-binding protein (mtSSB) ibophezela ku-DNA enomucu owodwa esanda kwakhiwa (ssDNA), iyivikele kuma-nuclease, futhi imise ukwakheka kwezakhiwo zesibili.
  • I-mtSSB isiza ukwenza i-mtDNA eyengeziwe ngokwenza umsebenzi we-TWINKLE we-helicase uqine futhi ngokwenza i-POLγ isebenze kakhulu.

Imodi ye-Mitochondrial DNA Replication (mtDNA)

  • Ngo-1972, uVinograd nozakwabo babonisa imodeli yokuthi i-mtDNA ikopisha kanjani. Imodeli yabo yokususa imicu ithi i-DNA yenziwa ngaso sonke isikhathi kuyo yomibili imicu ye-H- ne-L.
  • I-strand ngayinye, i-OH ne-OL, inephuzu layo lokuqala.
  • Okokuqala, ukuphindaphinda kuqala endaweni ye-OH, bese ukuhlanganiswa kwe-DNA kwenza i-H-strand entsha.
  • Phakathi nesigaba sokuqala, awekho ama-L-strand ayenziwa ngesikhathi esifanayo, futhi i-H-strand esusiwe, yabazali ihlanganiswe yi-mtSSB.
  • Ngokubophezela ku-DNA enomucu owodwa, i-mtSSB imisa i-mitochondrial RNA polymerase (POLRMT) kusukela ekuqaliseni ukuhlanganiswa kwe-RNA okungahleliwe kumucu osusiwe.
  • Uma imfoloko yokuphindaphinda isihambe cishe izingxenye ezimbili kwezintathu zendlela ku-genome, idlula umsuka wesibili wokuphindaphinda, OL.
  • Uma i-H-strand yabazali ku-OL iboniswa ngesimo sayo somucu owodwa, igoqa ibe isakhiwo se-stem-loop.
  • Isiqu simisa i-mtSSB ekubopheni kahle kakhulu, ngakho-ke ubude obufushane be-DNA enomucu owodwa endaweni yeluphu lusafinyeleleka. Lokhu kuvumela i-POLRMT ukuthi iqale ukwenza i-RNA.
  • I-POLRMT ayisebenzi kuzifanekiso ze-DNA ezinomucu owodwa kuphela. Ngemva cishe kwe-25 nt, i-POLγ ithatha indawo yayo, futhi i-L-strand DNA synthesis iyaqala.
  • Kusukela kuleli phuzu kuqhubeke, i-H-strand ne-L-strand synthesis iqhubeka kuze kube yilapho imicu emibili ihambe yonke indlela.
  • Ukuphindwaphindwa kwemicu emibili kuxhumene ngoba i-H-strand kumele yenziwe ngaphambi kokuba i-L-strand yenziwe.
  • Kokubili izifundo ze-vivo kanye ne-in vitro zesakhiwo nokulandelana kwezidingo ze-OL ezincelisayo zibonise ukuthi i-OL yomuntu esebenzayo kufanele ibe nesifunda esizinzile esinemicu ephindwe kabili enomucu wesifanekiso esinothile nge-pyrimidine kanye neluphu enentambo eyodwa okungenani yama-nucleotide ayi-10. (nt).
Imodi ye-Mitochondrial DNA Replication (mtDNA)
Ukuphindaphinda kwe-Mitochondrial DNA kuqaliswa e-OH futhi kuqhubeka ngokungaqondile ukukhiqiza i-H-strand yobude obugcwele. I-mtSSB ibopha futhi ivikele i-H-strand eveziwe, yomzali. Lapho impendulo idlula i-OL, kwakheka isakhiwo se-stem-loop esivimba ukubophezela kwe-mtSSB, kwethula indawo eyiluphu enomucu owodwa lapho i-POLRMT ingaqala khona ukuhlanganiswa kokuqala. Ukushintshela ku-L-strand DNA synthesis kwenzeka ngemva kwe-25 nt, lapho i-POLγ ithatha indawo ye-POLRMT ekupheleni kuka-3′-ekupheleni kwe-primer. Ukuhlanganiswa kwezintambo ezimbili kuqhubeka ngendlela eqhubekayo kuze kube yilapho sekwakhiwa ama-molecule amabili e-DNA agcwele, anemicu emibili.

Ukuphindaphinda kwe-genome ye-mitochondrial yomuntu

  • Ukuphindaphinda kwe-DNA ye-Mitochondrial kuqala ku-OH futhi kuya ohlangothini olulodwa kuze kube yilapho i-H-strand esafufusa igcwele ubude.
  • I-mtSSB ibophezela ku-H-strand yomzali eveziwe futhi iyigcine iphephile.
  • Lapho i-replisome idlula i-OL, kwenziwa isakhiwo se-stem-loop esivimbela i-mtSSB ekubopheni. Lokhu kushiya i-loop-region enomucu owodwa lapho i-POLRMT ingaqala khona ukwenza ama-primer.
  • Ngemva cishe kwe-25 nt, lapho i-POLγ ithatha indawo ye-POLRMT ekupheleni kuka-3′ we-primer, inqubo ishintshela ekwenzeni i-DNA ye-L-strand.
  • Le micu emibili yenziwa ngenqubo eqhubekayo kuze kube khona ama-molecule amabili e-DNA agcwele, anemicu ekabili.

Iyini i-D-loop?

Okuxakayo, akuyona yonke imicimbi yokuphindaphinda eqala ku-OH ebuyela lapho iqale khona. Esikhundleni salokho, u-95% usevele uphelile ngemuva kwe-650 nt ekulandeleni okubonisa ukuphela (TAS). Ucezu olufushane lwe-DNA olwenziwe ngale ndlela lubizwa ngokuthi i-7S DNA. Ihlala inamathele ku-L-strand yabazali, kodwa i-H-strand yabazali ihamba. Ngenxa yalokho, kwakhiwa isakhiwo se-D-loop, esakhiwe imicu emithathu yezihibe zokufuduka.

  • Akucaci ukuthi isakhiwo se-D-loop senzani, futhi akucaci ukuthi ukuphindaphinda kugcina kanjani ku-TAS.
  • Nokho, kubonakala sengathi ukuma e-TAS kuwumcimbi olawulwayo osebenza njengokushintsha phakathi kokuphindaphinda kwe-mtDNA okuphela kusenesikhathi kanye nokuphindaphinda okuhamba yonke indlela ku-genome.
  • Ukuhlaziywa kokuhlala kwe-vivo kubonise ukuthi i-POLγ iyayeka ukuhamba ekupheleni kwe-D-loop, kuyilapho ukuhlala kwe-TWINKLE kuphansi kule ndawo, okusekela lo mbono.
  • Lapho i-mtDNA isetshenziswa, isimo siyashintsha. Ukuhlala kwe-TWINKLE kuyenyuka, futhi amazinga e-7S DNA ehla ngesikhathi esifanayo.
  • Ngenxa yokuthi kunesidingo esiningi sokuphindaphinda kwe-mtDNA, le datha ibonwe njengobufakazi bokuthi i-TWINKLE ilayisha kabusha.
  • Uma i-helicase ibophezela ekugcineni okungu-3′ kwe-7S DNA, i-POLγ ebambekile ingaqhubeka nokukopisha i-7S DNA ize ingene esiyingini esigcwele.
  • Ukuhlolwa ngezakhi zofuzo zamagundane kusekela imodeli futhi kubonisa ukuthi i-TWINKLE ibalulekile ekulawuleni inani lamakhophi e-mtDNA. Uma amaleveli e-mtDNA enyuka noma ehla, kanjalo namazinga we-TWINKLE. Ngakho-ke, kungenzeka ukuthi ukuphindaphinda kwe-mtDNA kulawulwa ezingeni lokuqala esikhundleni sezinga lokuqala.
  • Iswishi ingakwazi ukulungisa inani lamakhophi e-mtDNA ngokusekelwe kulokho okudingwa yiseli ngalinye.
  • Ehlangothini ngalunye lwesifunda se-D-loop, kunezisusa zokulandelana ze-ATGN9CAT ezisondelene futhi ezihlale zingashintshile ngokuhamba kwesikhathi.
  • I-motif eyodwa iseduze nokuphela kwe-5′ kwe-7S DNA, lapho iyingxenye yokulandelana kwe-CSB1 (Ibhokisi Lokulandelana Okulondoloziwe 1).
  • I-motif yesibili, ebizwa ngokuthi i-core-TAS, isendaweni ye-TAS, ngemva nje kokuphela kwe-3′ ye-7S DNA (Umfanekiso 1, iphaneli ephezulu).
  • Namanje akukacaci ukuthi lezi motif zenzani emzimbeni, kodwa amaprotheni abophezela ku-DNA avame ukubona futhi abophe ukulandelana kwe-palindromic.
  • Izinyathelo ze-Organello zitholwe esifundeni se-TAS, esisekela lo mbono. Kodwa-ke, naphezu komsebenzi omningi kumalebhu ahlukene, iphrotheni ebopha i-TAS ayikatholakali.
  • Kungenzeka ukuthi izindlela zendabuko zenza kube nzima ukuhlanza amaprotheni abophezela ku-CSB1, i-core-TAS, nezinye izingxenye ze-TAS. Mhlawumbe iphrotheni elingekho linamathele kulwelwesi futhi kunzima ukuligcina linesixazululo ngesikhathi sechromatography.
  • Ukubopha kungase futhi kube inqubo elawulwayo edinga izimo ezithile ze-redox noma ukugxila kwe-nucleotide.
  • Okokugcina, ngeke kukhishwe ukuthi izakhiwo zesibili ku-mtDNA, njenge-stem-loops noma i-G-quadruplexes, nazo zingadlala indima futhi zengeze kuzinyathelo ze-DNA ezibonwa kumaseli aphilayo.

Ukuqaliswa kweMitochondrial DNA Replication (mtDNA) e-OH

  • Siyazi ukuthi ama-primer adingekayo ukuze kuqalwe ukuhlanganiswa kwe-H-strand OH kwenziwa yi-POLRMT.
  • Uma ukuloba kuqala ku-LSP, kwenziwa iziphetho ze-RNA 3, i-POL engayisebenzisa ukuqalisa ukuhlanganiswa kwe-DNA.
  • Ku-mitochondria yomuntu, kunezindawo ezimbalwa zokuguqula i-RNA-to-DNA ezitholakala ezansi nomfula we-LSP. Lawa maphuzu ahlanganiswe azungeze izisusa ezimbili zokulandelana ezilondoloziwe, i-CSB3 ne-CSB2.
  • Lezi zakhi zokulandelana ezilondoloziwe ziphezulu nge-guanine, futhi ukwakheka kwe-G-quadruplex kungakheka phakathi kwe-RNA entsha nomucu we-DNA ongabonisi isifanekiso ku-CSB2 ngesikhathi sokuloba.
  • Umbhalo omusha ube usunamathiselwa ku-mtDNA ngale ndlela, okwenza ukwakheka kwe-R-loop.
  • Isakhiwo se-G-quadruplex siphinde simise ukulotshwa ngaphambi kokuthi kufanele kumasayithi asesifundeni se-CSB2 afana namasayithi enguquko ye-RNA-to-DNA.
  • Ngokusekelwe kulawa maqiniso, bekucatshangwa ukuthi ukwakheka kokuqala e-OH kungase kubangelwe ukunqanyulwa kokuloba okuncike ngokulandelana.
  • Isici se-transcription elongation factor TEFM sehlisa kakhulu ukunqanyulwa kokuloba kanye nokwakheka kwe-R-loop ku-CSB2. Lokhu kuphakamisa ukuthi i-TEFM esebenzayo ingase iguqule isilinganiso phakathi kokwakheka kokuqala nobude obugcwele, ukuloba okukhiqizayo.
  • Futhi, abukho ubufakazi obuqondile obuvela ekuhlolweni bokuthi imibhalo ye-R-loop-forming ephela maduze ingasetshenziswa ngokuqondile yi-POLγ ukuze kuqalwe ukuhlanganiswa kwe-DNA.
  • Izindlela i-DNA replication eqala ngayo ku-OH ingase ifane nezindlela i-DNA replication eqala ngayo ku-E. coli plasmid ColE1.
  • Ku-plasmid, umbhalo we-RNAII ubophezela kumucu wesifanekiso ukwenza i-R-loop, esetshenziselwa ukuqala inqubo yokwenza i-DNA.
  • Futhi, umsuka we-ColE1 wokuphindaphinda utholakala ngemva kokunwebeka okucebile kwe-guanine okudingekayo kukho kokubili ukuqala kokuphindaphinda kanye nokwakhiwa kwe-R-loop.
  • I-RNase H isika i-ColE1 R-loop ngaphambi kokuthi isetshenziselwe ukuqala ukuhlanganiswa kwe-DNA. Namanje akwaziwa ukuthi i-mitochondrial RANSEH1 idlala indima efanayo kumaseli ezincelisayo.

Ukuqedwa kweMitochondrial DNA Replication (mtDNA)

  • I-DNA ligase III ihlanganisa imicu ye-DNA entsha ngemva kokuba i-POLγ isiqedile ukuyenza.
  • Ukuze i-ligation isebenze kahle, iziphetho ezi-5 kanye nezi-3 ze-DNA entsha kufanele zibekwe eduze komunye nomunye. Lokhu kusho ukuthi iziqalo ze-RNA ezasetshenziswa ukuqala ukuhlanganiswa kwe-mtDNA kumele zikhishwe kuqala.
  • I-RNASEH1 kungenzeka iyikhandidethi lokususwa kwe-primer ngoba ama-primers e-RNA asatholakala ezindaweni zomsuka we-mitochondrial we-mouse embryonic fibroblasts angenayo i-Rnaseh1 kanye ne-Rnaseh1 knockout amagundane alahlekelwa yi-mtDNA yawo.
  • Ngemva kokuphindaphinda kwendingilizi egcwele, i-POLγ ihlangana nesiphetho esingu-5 somucu we-mtDNA wobude obugcwele esanda kuwenza.
  • Kuleli qophelo, i-POLγ iqala umjikelezo wokuwohloka kwe-exonuclease engu-3–5 kanye ne-polymerization ku-nick. Idling kuyinqubo okumele yenzeke ukuze i-ligation isebenze kahle.
  • I-POLγ engenawo umsebenzi we-exonuclease ayikwazi ukuyeka ukwenza i-DNA. Esikhundleni salokho, iqhubeka nokwenza i-DNA endaweni ye-dsDNA idlule isiphetho esingu-5, yenza isakhiwo esifana ne-flap esingakwazi ukuhlanganiswa.
  • Iqiniso lokuthi amagundane ane-POLγ entula i-exonuclease anama-nick akhethekile ku-OH kungase kubangelwe ukungakwazi ukwenza iziphetho ze-DNA ezingahlanganiswa ndawonye.
  • Ngokushintshashintsha okuthakazelisayo, kukhona isiphetho esikhulu esingu-5 se-DNA esanda kuzalwa cishe nge-100 bp ngemva kwezindawo zoshintsho ze-RNA-to-DNA ezitholiwe.
  • Ngisho noma bekucatshangelwa ukuthi isiphetho samahhala esingu-5 endaweni engu-191 yilapho kwaqala khona ukuphindaphinda kwe-mtDNA, kungenziwa ngezinye izindlela. Isibonelo, i-H-strand esanda kuzalwa ingase idlule ekucubunguleni okuningi kwe-5′-end lapho i-primer isusiwe. Akukhona nje kuphela ukuthi i-primer ye-RNA isusiwe, kodwa futhi cishe ne-100 nt ye-DNA iqhubekela phansi phansi.
  • Lokhu kuzohlukanisa indawo lapho i-RNA iphenduka i-DNA endaweni lapho ama-H-strands asanda kuhlanganyela ahlangana khona ekupheleni kokuphindaphinda.
  • I-mitochondrial genome maintenance exonuclease 1 (MGME1), i-RecB-type exonuclease ku-mitochondria eyingxenye ye-PD-(D/E) XK nuclease superfamily, ingaba imbangela yalo mphumela.
  • Amaseli omuntu angenayo i-MGME1 esebenzayo anenkinga yokujoyina e-OH futhi enze ama-molecule e-mtDNA asusiwe ahlanganisa i-OH ne-OL. Kukhona futhi ama-molecule e-DNA angu-7S amaningi kunangaphambili.
  • Iziphetho ezi-5 zale mikhiqizo ye-7S DNA ziseduze ne-CSB2 kunamaseli avamile, okuphakamisa ukuthi i-MGME1 ihileleke ekucubunguleni i-5-end ye-H-strand entsha.

Ukuhlukaniswa kwe-Mitochondrial DNA (mtDNA)

  • Ngesikhathi sokuphindaphinda kwe-DNA, i-molecule yokuqala ihlala ifana, okubangela inkinga emshinini onyakazayo owenza ukuphindaphinda.
  • Ngokuvumela enye yezintambo ukuthi idlule kwenye, thayipha i-topoisomerase yoku-1 ingakhulula ubunzima obubangelwa yilokhu.
  • Ku-mitochondria yezilwane ezincelisayo, uhlobo lwe-enzyme ye-IB olubizwa ngokuthi i-TOP1MT lungasebenza ne-mitochondrial replisome “njenge-swivel” ye-DNA. Lapho isakhi sofuzo se-Top1mt sikhishwa egundaneni, sikhiqiza inzalo ephilayo ene-mtDNA supercoiling ehlukile.
  • Kwezinye izinhlelo, uma iphelele, i-DNA eyindilinga ikopishwa, yenza ama-molecule endodakazi axhunywe ndawonye njengama-catenanes. Lokhu kusho ukuthi imibuthano ye-DNA ayikaqedwa.
  • Ngakho-ke, ukuze kuhlukaniswe ngokuphelele ama-molecule endodakazi, ukuphindaphinda kwama-genomes ayindilinga kudinga ukuhlukaniswa.
  • Ukuxazulula isakhiwo se-hemicatenane, i-isoform ye-mitochondrial ye-Topoisomerase 3αα (Top3) iyadingeka. Ukulahlekelwa kwe-Top3α kubangela ukuthi i-mtDNA yehle futhi yakhe amanethiwekhi amakhulu e-mtDNA exhunyiwe.
  • Iqiniso lokuthi ama-hemicatenanes abamba lawa manethiwekhi e-mtDNA ndawonye aku-OH-region liyathandeka. Lokhu kusikisela ukuthi lezi zakhiwo zenziwa lapho ukuphindaphinda kwe-mtDNA sekuqediwe.
  • Ngisho noma i-Top3 idingeka ukuze kuhlukaniswe i-mtDNA esanda kukopishwa, kungenzeka ukuthi namanye amaprotheni nawo ayadingeka.
  • Kukhona inguqulo yenuzi ye-Top3 esebenza namanye amaprotheni amathathu: i-helicase BLM kanye ne-OB-fold proteins i-RMI1 ne-RMI2.
  • Ehlangene, lawa maprotheni enza inkimbinkimbi ye-BTR, ehlukanisa i-Holliday junctions ephindwe kabili. Ukuze i-Top3 yenze umsebenzi wayo njenge-topoisomerase, idinga amanye amayunithi amancane.
  • Kodwa njengoba i-BLM noma i-RMI1 noma i-RMI2 ingenayo i-isoform ye-mitochondrial, amanye amaprotheni angase asebenze ne-Top3 ku-mitochondria ukulawula kanye/noma ukusheshisa umsebenzi wayo.
Ukuhlukaniswa kwe-Mitochondrial DNA (mtDNA)
Ngemuva kokuphindaphinda kwe-mtDNA, ama-molecule endodakazi entsha axhunywa ngomshini ngesakhiwo se-hemicatenane, esidinga ukuthi i-Top3α ixazululwe.

Ukuphindaphinda kwe-Nucleoid

  • I-mtDNA ayiyona i-molecule eyodwa. Kunalokho, iyingxenye yama-nucleoprotein complexes amakhulu okuthiwa ama-nucleoid. Kunezindlela ezahlukene zokusebenzisa i-fluorescent microscopy ukuze ubone ama-nucleoid.
  • Isilinganiso sobukhulu be-nucleoid singaba ngu-100 nm, futhi isikhathi esiningi kuba ne-molecule ye-mtDNA eyodwa kuphela nge-nucleoid.
  • Iprotheyini yesakhiwo ebaluleke kakhulu ku-nucleoid ibizwa nge-TFAM. Ineyunithi eyodwa yawo wonke u-16–17 bp we-mtDNA.
  • I-TFAM iyilungu lomndeni wesizinda sebhokisi le-HMG, futhi ingabophezela ku-DNA kungakhathaliseki ukuthi ilandelana kanjani.
  • I-TFAM futhi iyingxenye ebalulekile yomshini olawula ukuloba ku-mitochondria.
  • Ngesikhathi sokuqala kokubhala, iphrotheni ibophezela phezulu kwendawo yokuqala yokubhala futhi yenza i-DNA igobe ngokucijile.
  • Ngokuxuba i-TFAM ne-mtDNA, izinhlayiya ezinjenge-nucleoid zingenziwa futhi. Lokhu kuphakamisa ukuthi i-TFAM ingakwazi ukuhlanganisa i-mtDNA ngokugcwele iyodwa.
  • I-TFAM inezindawo ezimbili lapho ingabopha khona ku-DNA, futhi ibonakala yenza i-mtDNA ihlangane ngokuhlanganisa imicu kanye nokwenza izihibe.
  • I-TFAM iphinde isebenze namanye amaprotheni ukuze ibophezele ku-DNA, yenza ama-protein patches ku-mtDNA.
  • Umbono wokuthi i-TFAM ilawula ukuphindaphinda kwe-mtDNA ngokusebenzisa i-epigenetics uyathakazelisa kakhulu.
  • I-Super-resolution microscopy ibonise ukuthi ama-nucleoid eza ngezindlela ezihlukene. Mhlawumbe ama-nucleoid amancane ayindlela yokugcina i-mtDNA, kuyilapho amakhulu esebenza ngokuphindaphinda kanye/noma ekulotshweni.
  • Ama-nucleoid abandakanyeka ekuphindaphindeni kwe-DNA esebenzayo atholwe ezindaweni lapho i-endoplasmic reticulum (ER) ihlangana ne-mitochondria. Kulezi zindawo, i-mitochondria iyahlukana, okuholela embonweni wokuthi ukuxhumana phakathi kwe-endoplasmic reticulum ne-mitochondria kungaxhumanisa ukuhlanganiswa kwe-mtDNA ngokuhlukana ukuze kuqinisekiswe ukuthi ama-nucleoid asanda kwenziwa asabalaliswa ngokulinganayo kunethiwekhi ye-mitochondrial.
  • Izinguquko ezincane esilinganisweni se-TFAM ne-DNA eshubhuni yokuhlola zingaba nemiphumela emikhulu. Ezilinganisweni ze-physiological, kunomehluko omkhulu endleleni i-mtDNA egcwele ngayo, futhi kokubili ama-nucleoid agcwele ngokugcwele kanye ne-DNA enqunu ingabonakala ngesikhathi esisodwa.
  • Ngaphansi kwalezi zimo, ukukhuphuka okuncane kwenani le-TFAM kungenza umehluko omkhulu ekutheni mangaki ama-molecule e-mtDNA ahlanganiswe ngokugcwele.
  • Le modeli ichaza ukuthi kungani inani le-TFAM ku-vivo lihlala licishe lilingane nenani le-mtDNA. Iphinde iphakamise ukuthi izinguquko ezincane enanini le-TFAM zingaba nemiphumela emikhulu kukho kokubili ukubonakaliswa kofuzo nokuphindaphinda kwe-mtDNA.
  • Lo mbono usekelwa iqiniso lokuthi amapeshi amade e-TFAM amisa i-DNA ukuthi ingavuleki, okuvimba ukuphindaphinda kwe-mtDNA kanye nemishini yokubhala ukuthi iye phambili.
  • Ngakho-ke, i-TFAM ingase ibe isilawuli se-epigenetic esilawula inani lama-molecule e-mtDNA angasetshenziselwa ukuloba okusebenzayo kanye/noma ukuphindaphinda kwe-mtDNA.

Keynote

  • I-mtDNA ezilwaneni ezincelisayo iphindaphindwa ngamaprotheni ahlukene kulawo asetshenziselwa ukuphindaphinda kwe-nuclear DNA.
  • Ngokuvumelana nomqondo wokufuduka kwe-strand, ukuphindaphinda kuqala emisuka emibili ehlukene, OH kanye no-OL.
  • I-primer esetshenziswa yi-POL ukuze icuphe ukuhlanganiswa kwe-DNA e-OH ithathwe emibhalweni eqalwe yi-LSP.
  • I-OL ikhiqiza ukwakheka kwe-stem-loop, futhi i-POLRMT iqala ukukhiqizwa kokuqala endaweni eyiluphu ye-DNA enomucu owodwa.
  • Umsebenzi we-mitochondrial D-loop awaziwa.
  • I-RNASEH1 kanye ne-MGME1 idlala indima ebalulekile ekuqedeni i-primer, kodwa imininingwane yalo mshini ihlala ingacacile.
  • I-Top3α iyadingeka ukuze kuxazululwe izakhiwo ze-hemicatenane phakathi kwama-molecule e-mtDNA asanda kuphindaphindwa.
  • I-mtDNA ayiyona i-molecule entantayo mahhala, kodwa kunalokho ifakwe kuma-nucleoprotein complexes abizwa ngokuthi ama-nucleoid.
  • I-mtDNA synthesis ixhunyaniswe nokuhlukaniswa kwe-mitochondrial.

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