RNA cuam tshuam dab tsi? Lo lus no yog hais txog lub kaw lus rau kev tswj cov kev ua ntawm cov noob hauv eukaryotic hlwb. Cov txheej txheem zoo sib xws tshwm sim vim luv luv (tsis pub ntau tshaj 25 nucleotides ib txoj saw) molecules ntawm ribonucleic acid.
RNA cuam tshuam yog tus cwj pwm los ntawm kev cuam tshuam tom qab transcriptional inhibition ntawm cov noob qhia los ntawm kev puas tsuaj lossis kev tuag ntawm mRNA.
Qhov tseem ceeb
Nws tau pom nyob rau hauv lub hlwb ntawm ntau eukaryotes: fungi, nroj tsuag, tsiaj.
RNA cuam tshuam yog suav tias yog txoj hauv kev tseem ceeb los tiv thaiv cov hlwb los ntawm cov kab mob. Nws koom nrog cov txheej txheem ntawm embryogenesis.
Vim qhov muaj zog thiab xaiv qhov tshwm sim ntawm cov nyhuv ntawm ribonucleic acid ntawm cov noob qhia, kev tshawb fawb lom neeg loj tuaj yeem ua tiav hauv cov kab mob muaj sia, kab lis kev cai ntawm tes.
Yav dhau los, RNA cuam tshuam muaj lub npe txawv - kev tawm tsam. Tom qab kev kawm ntxaws ntxaws ntawm cov txheej txheem no, tau txais Nobel nqi zog hauv Tshuaj rau kev kawm txog cov txheej txheem ntawm nws qhov tshwm sim los ntawm Andrew Fire thiab Craig Melo, cov txheej txheem no tau hloov npe.
History
RNA cuam tshuam dab tsi? Nws qhov kev tshawb pom yog vim qhov kev soj ntsuam ua ntej loj nyob rau hauv kev cuam tshuam ntawmAntisense RNA inhibition ntawm kev qhia hauv cov noob noob.
Qee lub sij hawm tom qab, cov kws tshawb fawb Asmeskas tau txais txiaj ntsig zoo thaum transgenes tau nkag mus rau hauv petunias. Cov kws tshawb fawb tau sim hloov kho cov tshuaj ntsuam xyuas cov nroj tsuag hauv txoj hauv kev kom muab cov paj kom muaj xim ntau dua. Ua li no, lawv tau nkag mus rau hauv lub hlwb ntxiv cov ntawv luam ntawm cov noob rau cov enzyme chalcone synthase, uas yog lub luag haujlwm rau kev tsim cov xim liab.
Tab sis cov txiaj ntsig ntawm txoj kev tshawb fawb tsis tuaj yeem pom tau. Es tsis txhob qhov xav tau darkening ntawm corolla ntawm petunia, paj ntawm cov nroj tsuag no tau ua dawb. Kev txo qis ntawm cov enzyme chalcone synthase tau raug hu ua cosuppression.
cov ntsiab lus tseem ceeb
Ua raws li cov kev sim no tau nthuav tawm cov txiaj ntsig ntawm cov txheej txheem tom qab kev hloov pauv hloov pauv ntawm cov noob qhia vim qhov nce qib ntawm mRNA degradation.
Thaum lub sijhawm ntawd nws paub tias cov nroj tsuag uas qhia cov protein tshwj xeeb tsis muaj kev cuam tshuam los ntawm tus kabmob. Nws tau raug sim tsim kom tau txais qhov kev tiv thaiv no yog ua tiav los ntawm kev qhia luv luv uas tsis yog-coding ib ntus ntawm tus kab mob RNA rau hauv cov noob noob.
RNA cuam tshuam, cov txheej txheem uas tseem tsis tau nkag siab tag nrho, tau raug hu ua "tus kab mob-induced noob silence."
Biologists pib hu rau cov txiaj ntsig ntawm qhov tshwm sim tom qab transcriptional inhibition ntawm noob qhia.
Andrew Hluav Taws thiab nws cov npoj yaig tau tswj hwm los ua pov thawj qhov kev sib txuas ntawm qhov tshwm sim zoo sib xws thiab kev qhia txog cov txheej txheem semanticRNA thiab antisense tsim ob-stranded RNA. Nws yog nws leej twg tau lees paub tias yog lub hauv paus tseem ceeb rau qhov tshwm sim ntawm cov txheej txheem piav qhia.
Txoj kev ntawm molecular mechanisms
Lub Giardia plab hnyuv Dicer protein yog catalyzed los ntawm kev txiav ob-stranded RNA los tsim me me interfering RNA fragments. Lub RNAase domain yog ntsuab, PAZ domain yog daj, thiab khi helix yog xiav.
Daim ntawv thov ntawm RNA cuam tshuam yog raws li txoj hauv kev exogenous thiab endogenous.
Thawj txheej txheem yog raws li tus kab mob genome lossis yog qhov tshwm sim ntawm kev sim hauv chav sim. Xws li RNA raug txiav rau hauv cov khoom me me hauv cytoplasm. Hom thib ob yog tsim thaum lub sijhawm qhia ntawm tus kheej cov noob ntawm cov kab mob muaj sia, piv txwv li, pre-micro RNA. Nws koom nrog kev tsim cov qauv qia-voj hauv lub nucleus, tsim mRNAs uas cuam tshuam nrog RISC complex.
Kev cuam tshuam me me RNAs
Lawv yog chains muaj 20-25 nucleotides nrog nucleotide protrusions ntawm qhov kawg. Txhua lub saw muaj hydroxyl moiety ntawm 3' kawg thiab phosphate pawg ntawm 5' moiety. Ib qho qauv ntawm hom no yog tsim los ntawm kev ua ntawm Dicer enzyme ntawm RNA uas muaj cov plaub hau. Tom qab cleavage, cov fragments ua ib feem ntawm lub catalytic complex. Cov argonaut protein maj mam unwinds RNA duplex, uas ua rau tsuas yog ib qho "qhia" strand hauv RISC. Nws tso cai rau lub effector complex mus nrhiav ib lub hom phiaj mRNA. Thaum koomsiRNA-RISC complex mRNA degradation tshwm sim.
Cov molecules hybridize nrog ib hom phiaj mRNA, ua rau cleavage ntawm molecule.
mRNA
RNA cuam tshuam thiab kev tiv thaiv cov nroj tsuag yog cov txheej txheem cuam tshuam.
mRNA muaj 21-22 sib law liag nucleotides ntawm endogenous keeb kwm, uas koom nrog hauv cov txheej txheem ntawm tus kheej kev loj hlob ntawm cov kab mob. Nws cov noob tau sau tseg los ua cov ntawv sau ntev ntawm pri-miRNA transcripts. Cov qauv no muaj daim ntawv qia-voj, lawv qhov ntev muaj 70 nucleotides. Lawv muaj ib qho enzyme nrog RNase kev ua, nrog rau cov protein muaj peev xwm los khi ob-stranded RNA. Tsis tas li ntawd, kev thauj mus los rau cytoplasm yuav siv qhov chaw, qhov twg RNA ua rau lub substrate rau Dicer enzyme. Kev ua tiav yuav tshwm sim hauv ntau txoj kev, nyob ntawm seb hom ntawm tes.
Qhov no yog RNA cuam tshuam ua haujlwm li cas. Daim ntawv thov txheej txheem tseem tsis tau tshawb pom tag nrho.
Piv txwv li, nws muaj peev xwm tsim tau txoj hauv kev sib txawv ntawm mRNA ua, uas tsis nyob ntawm Diser. Hauv qhov no, molecule raug txiav los ntawm argonaut protein. Qhov sib txawv ntawm miRNA thiab siRNA yog lub peev xwm los cuam tshuam kev txhais lus nrog ntau mRNAs uas muaj cov amino acid zoo sib xws.
RISC effector complex
RNA cuam tshuam,cov kev ua haujlwm lom neeg uas tso cai rau kev daws teeb meem ntau yam cuam tshuam nrog cov protein complex, uas ua kom cov cleavage ntawm mRNA thaum cuam tshuam. Lub RISC complex txhawb kev faib ntawm ATP rau hauv ntau qhov tawg.
Nrog kev pab ntawm X-ray diffraction tsom xam, nws tau txiav txim siab tias los ntawm txoj kev ua haujlwm nyuaj no tau nrawm dua. Nws qhov catalytic yog suav tias yog argonaut proteins, uas yog nyob hauv qee qhov chaw hauv cytoplasm. Xws li P-lub cev sawv cev rau thaj chaw uas muaj theem tseem ceeb ntawm RNA degradation; nws yog nyob rau hauv lawv qhov siab tshaj plaws mRNA kev ua haujlwm tau kuaj pom. Kev puas tsuaj ntawm cov complexes yog nrog los ntawm kev txo qis hauv kev ua haujlwm ntawm RNA cuam tshuam txheej txheem.
Txoj kev ntawm kev tshem tawm kev txwv
Ntxiv rau nws qhov kev ua ntawm qib ntawm kev txhais lus inhibition, RNA kuj muaj txiaj ntsig ntawm cov noob hloov pauv. Qee cov eukaryotes siv txoj kev no los xyuas kom meej qhov ruaj khov ntawm cov qauv genome. Ua tsaug rau kev hloov kho ntawm histones, nws muaj peev xwm txo tau cov noob qhia nyob rau hauv ib qho chaw, vim hais tias xws li ib daim hla mus rau hauv daim ntawv ntawm heterochromatin.
RNA cuam tshuam thiab nws lub luag haujlwm lom neeg yog qhov teeb meem tseem ceeb uas tsim nyog tau txais kev kawm thiab tshuaj xyuas. Txhawm rau ua kev tshawb fawb, cov ntu ntawm cov saw hlau uas muaj lub luag haujlwm rau hom kev sib txuas yog txiav txim siab.
Piv txwv li, rau cov poov xab, kev tshem tawm cov kev txwv yog ua tiav los ntawm RISC complex, uas muaj cov Chp1 feem nrog chromodomain, argonaut, thiab cov protein uas muaj. Unknown function Tas3.
txhawm rau txhawm rau tsim cov cheeb tsam heterochromatin, Dicer enzyme, RNA polymerase, yuav tsum tau ua. Kev faib tawm ntawm cov noob no ua rau muaj kev ua txhaum ntawm histone methylation, ua rau qeeb hauv cell faib, lossis ua tiav ntawm cov txheej txheem no.
RNA kho kho
Cov txheej txheem ntau tshaj plaws ntawm cov txheej txheem no hauv cov eukaryotes siab dua yog cov txheej txheem ntawm kev hloov adenosine rau inosine, uas tshwm sim hauv ob txoj hlua ntawm RNA. Txhawm rau ua qhov kev hloov pauv no, siv cov enzyme adenosine deaminase.
Thaum pib ntawm nees nkaum-thawj xyoo pua, qhov kev xav tau muab tso rau pem hauv ntej, raws li qhov no, cov txheej txheem ntawm RNA cuam tshuam thiab kho cov molecule tau lees paub tias yog cov txheej txheem sib tw. Cov kev tshawb fawb mammalian qhia tias kev kho RNA tuaj yeem tiv thaiv transgene silence.
Qhov txawv ntawm kab mob
Nws nyob hauv lub peev xwm los nkag siab txog RNA txawv teb chaws, siv lawv hauv kev cuam tshuam. Rau cov nroj tsuag, cov nyhuv no yog systemic. Txawm hais tias muaj qee qhov kev taw qhia me ntsis ntawm RNA, qee cov noob raug tshem tawm thoob plaws hauv lub cev. Nrog rau qhov kev txiav txim no, RNA teeb liab kis ntawm lwm lub hlwb. RNA polymerase koom nrog hauv nws qhov kev nthuav dav.
Ntawm cov kab mob muaj qhov sib txawv ntawm kev siv cov noob txawv teb chaws hauv cov txheej txheem ntawm RNA cuam tshuam.
Hauv cov nroj tsuag, cov txheej txheem ntawm siRNA thauj tshwm sim los ntawm plasmodesmata. Qhov qub txeeg qub teg ntawm cov teebmeem RNA no yog ua kom ntseeg tau los ntawm cov tshuaj methylation ntawm cov neeg txhawb nqa ntawm qee cov noob.
Qhov sib txawv tseem ceeb ntawm cov txheej txheem no thiabcov nroj tsuag yog qhov zoo tshaj plaws ntawm lawv cov mRNA complementarity, uas, ua ke nrog RISC complex, pab ua kom tiav degradation ntawm no molecule.
Biological functions
Lub kaw lus nug yog ib qho tseem ceeb ntawm lub cev tiv thaiv kab mob rau cov khoom txawv teb chaws. Piv txwv li, cov nroj tsuag muaj ntau yam analogues ntawm Dicer protein, uas yog siv los tua ntau yam kab mob.
RNA tuaj yeem suav hais tias yog tsob nroj tau txais cov tshuaj tiv thaiv kab mob uas tshwm sim thoob plaws lub cev.
Txawm tias qhov tseeb tias Dicer protein ntau tsawg tau qhia hauv cov tsiaj txhu, peb tuaj yeem tham txog kev koom tes ntawm RNA hauv cov tshuaj tiv thaiv kab mob.
Tam sim no, cov tshuaj tiv thaiv kab mob tshwm sim hauv lub cev ntawm tib neeg thiab tsiaj txhu tau kawm ib nrab.
Biologists txuas ntxiv kev tshawb fawb, sim tsis tsuas yog ua kom pom tseeb cov txheej txheem ntawm lawv qhov tshwm sim, tab sis kuj nrhiav txoj hauv kev los cuam tshuam kev tiv thaiv kab mob. Nyob rau hauv rooj plaub ntawm kev piav qhia ua tiav ntawm tag nrho cov nuances ntawm RNA cuam tshuam, cov kws tshawb fawb yuav muaj peev xwm tswj tau cov tshuaj biochemical thiab tsim cov txheej txheem ntawm kev tiv thaiv lub cev txawv teb chaws.
