第七章 RNA Processing In both prokaryotes and eukaryotes, primary RNA transcripts undergo various alteration or processing events to become mature rNAs: The three commonest types are: 1, nucleotide removal by nucleases 2, nucleotide addition to the 5-or 3-end, 3. nucleotide modification on the base or the sugar
第七章 RNA Processing In both prokaryotes and eukaryotes, primary RNA transcripts undergo various alteration or processing events to become mature RNAs: The three commonest types are: 1, nucleotide removal by nucleases; 2, nucleotide addition to the 5’- or 3’-end, 3, nucleotide modification on the base or the sugar
第一节 rRNa processing and ribosomes rrNa processing in prokaryotes 1 Seven different operons for rrNA dispersed thought out the genome. 2\ The primary transcript is 30S (6000nt 3 Each contains one copy of 5s, 16s and 23S rRNA, together with some tRNA sequence. 4 Rnase il is involved in rrna processing
第一节 rRNA processing and ribosomes 一、rRNA processing in prokaryotes 1、 Seven different operons for rRNA dispersed thought out the genome. 2、The primary transcript is 30S (~6000nt). 3、 Each contains one copy of 5S,16S and 23S rRNA, together with some tRNA sequence. 4、 Rnase III is involved in rRNA processing
30s transcript fizEp4l gif
30S transcript
Primary rrNa processing in prokaryotes Pre-16S rRNA Pre-t RNa Pre-23S rRNA Pre-tRNA Pre-5SrRNA Primary transcript RNase Precursors MaturerrNa
Primary rRNA processing in prokaryotes Pre-16S rRNA Pre-t RNA Pre-23S rRNA Pre-tRNA Pre-5S rRNA Precursors Mature rRNA Primary transcript RNase
5, The rRNa folds up into stem-loop structures by base pairing in the transcript 6 Srrna的二级结构 5 end 3 major doma 3 end 5 domain 3 minor domain m
16S rRNA的二级结构 5、The rRNA folds up into stem-loop structures by base pairing in the transcript
6 Some specific proteins bind to the rrNa to form rNP complex TRNA Proteins Subunits Assembled ▲△△ △ 23s 55 12900 bases (120 bases (Total: 31 S1 S2 S3 ●oo Q 11540bas0s Total: 21) 30s L1 L2 L3 △▲ 当 △ 28s:58s △ G (4800 bases-160 bases)(120 bases (Total: 50) S1 S2 S3 2 ● 18s (1900 bases
6、 Some specific proteins bind to the rRNA to form RNP complex
30S亚基的三维结构 CP st A L1
30S 亚基的三维结构
二、 rRNA processing in eukaryotes I, In the nucleolus, rNa polymerase I transcribes the rRNA, which usually exist in tandem repeats containing 100 or more copies of the transcription units 2 Primary transcript 47s, containing ETS external transcribed sequence ITs internal transcribed sequence ETS ITS ETS Pre-I8S Pre-58S Pre-28S
二、rRNA processing in eukaryotes 1、In the nucleolus, RNA polymerase I transcribes the rRNA, which usually exist in tandem repeats containing 100 or more copies of the transcription units . 2、 Primary transcript 47S, containing ETS external transcribed sequence ITS internal transcribed sequence ETS ITS ITS ETS Pre-18S Pre-5.8S Pre-28S
RNP(ribonucleoproteins) RNA-Protein complexes 3 The precursor folds and complexes with proteins as it is being transcribed in the nucleolus 4 Many specific ribose methylations take place at over 100 sites and is carried out directly by a subset of snRNP particles 5 snRNPs contain snrnas that have short streches of complementarity to parts of the rrna and, by base pairing with it, they define where methylation takes place
3、 The precursor folds and complexes with proteins as it is being transcribed in the nucleolus. 4、Many specific ribose methylations take place at over 100 sites and is carried out directly by a subset of snRNP particles. 5、snRNPs contain snRNAs that have short streches of complementarity to parts of the rRNA and, by base pairing with it, they define where methylation takes place. RNP(ribonucleoproteins)： RNA-Protein complexes
、核糖体。由两个亚基组成,每个亚基由 数十个蛋白质和3-4种rRNA组成。 Ribosomes Subunits TRNAS Proteins Bacterial 23S= 2904 bases 5S= 120 bases mas:2.5X10°D 66% RNA 16S= 1542 bases 21 30 28S= 4718 bases 5.8s= 160 bases 5S= 120 bases mass: 4.2X 10D 60% RNA 18S= 1874 bases
三、核糖体。由两个亚基组成，每个亚基由 数十个蛋白质和3－4种rRNA组成