原核(Porkaryotes) | 真核(Eukaryotes) | |
---|---|---|
DNA合成酶(DNA Polymerase) | 有三種:
|
只有一種DNA polymerase
|
RNA合成酶(RNA polymerase | 只有一種
|
有三種
|
轉錄(Transcription) | ||
起始(Initiation) | σ辨識啟動子(Promoter)→Closed-promoter complex→open promoter complex→mRNA合成(第一個是嘌呤pruine)→做10個後丟掉→σ離開→正式做mRNA
Promoter:-35區域 至 -10區域 |
Pol I promoter: upstream promoter, core promoter
兩個輔因子:
|
Pol II promoter: TATA box(-25)
Transcription factor:TBP and TFIID(enhancer, response element) | ||
Pol III promoter: downstream of star point(+55)-box A and boxC
Transcription factor: TFIIIB and TFIIIC | ||
終止(Termination) | Factor independent: GC rich→stem loop→mRNA上出現U-rich→release
Factor dependent:ρ factor attenuation |
Pol II 在mRNA上做出AAUAA之後,繼續往下移動,但在之後的11到30個base位置被endonuclease切掉,由poly(A) polymerase加上polyA |
轉譯(Translation) | ||
起始 | SD sequence, start condon|)→50S→release IF1, 2, 3
第一個胺基酸: N-formylmethionine SD sequence:AGGAGG,位於<10 base upstream |
Small subunit 和cap結合後,開始往3'移動,找到AUG後,large unit與small unit結合,開始轉錄eIF1, eIF1A, eIF2, eIF2B, eIF3, eIF4C, eIF4A, eIF4B, eIF4F, eIF5, eIF6
第一個胺基酸:methionine |
延長因子(elongation factors) |
|
|
終止(Termination) | UAA, UAG, UGA | UAA, UAG, UGA |
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