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
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
Primary rRNA processing in prokaryotes
Pre-16S rRNA Pre-5S rRNAPre-t RNA Pre-23S rRNA Pre-tRNA
Precursors
Mature rRNA
Primary
transcript
RNase
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
30S 亚基的三维结构
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
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
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。
第二节 tRNA Processing,
RNaseP and ribozymes
1,In prokaryotes,mature tRNA are
generated by processing longer pre-tRNA
transcripts by RNases D,E,F and P,
followed by base modification which are
unique to each particular tRNA type.
一, tRNA processing
2,In eukaryotes,pre-tRNAs are
synthesized with an intron as well
as extra 5’ and 3’ nucleotides which
are all removed during processing,
The 3’-terminal CCA is added by
transferase.
Many base modification also occur.
二,RNaseP 核糖核酸酶 P
1,RNaseP is endonuclease composed of one RNA
molecules and one protein molecules,It is a simple
RNP.
2 RNaseP are found both in prokaryotes and
eukaryotes.
3 The RNA component alone works as an
endonuclease,This RNA is a catalytic RNA,or
ribozyme.
三,Ribozyme
1 Definition,
Ribozyme is a catalytic RNA molecules that
catalyze particular biochemical reactions in
the absence of protein.
2 Examples,The self-splicing of the large subunit
of rRNA in Tetrahymena;
3 ’ G -O H H O -CCCCCCp 3 ’ G
C-O H
5 ’ p CCCCC-O H 3 ’ 5 ’ p CCCCC-O H 3 ’
G G G A G G 5 ’ G G G A G G 5 ’
C 5 与 I G S 位点附近的 RN A 5 ’ 端配对 另一轮 C 5 转移反应开始,释放 C 6
3 ’ G -O H 3 ’ G
C-O H
5 ’ p CCCCC-O H 3 ’
G G G A G G 5 ’ G G G A G G 5 ’
H O -CCCCp
G - O H 攻击 Cp C 键 C 被转移到 3 ’－ G 上； C4 被释放
图 1 3 - L -1 9 RN A 具有催化 C 6 合成的能力
The concatenmeric molecules of the RNA genome
of plant viruses are able to fold up to self-cleave
themselves into monomeric genome-sized length.
3 Application,
The minimum sequences needed for self-
cleaving are identified and applied to inhibit
gene expression by cleaving mRNA molecules,It
may be possible to
prevent virus replication,
kill cancer cells,
discover the function of new
genes by inactivating them.
茎 3
3 ’ 5 ’
剪切
C G
A U
A N
A
G N C G N N N N N
C N G N N N N N
A C
G U
N G
茎 2 A 茎 1
催化位点
图 13 － 锤头结构含 5 8 n t,有 3 个茎环和 13 碱基
的保守顺序 ( G E N E S V I F i g 3 1, 1 2 )
C
底物链 C G
A U 剪切
C G
A U
A C
A
P p p G C G C C G U C G A G C OH
O H C G C G G A G C U C G G ppp
A C
G U
U G
A
催化链
图 1 3 - 两条互补的 R N A 相互作用也可形成锤头结构
( G E N E S V I F i g 3 1, 1 2 )
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
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
Primary rRNA processing in prokaryotes
Pre-16S rRNA Pre-5S rRNAPre-t RNA Pre-23S rRNA Pre-tRNA
Precursors
Mature rRNA
Primary
transcript
RNase
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
30S 亚基的三维结构
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
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
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。
第二节 tRNA Processing,
RNaseP and ribozymes
1,In prokaryotes,mature tRNA are
generated by processing longer pre-tRNA
transcripts by RNases D,E,F and P,
followed by base modification which are
unique to each particular tRNA type.
一, tRNA processing
2,In eukaryotes,pre-tRNAs are
synthesized with an intron as well
as extra 5’ and 3’ nucleotides which
are all removed during processing,
The 3’-terminal CCA is added by
transferase.
Many base modification also occur.
二,RNaseP 核糖核酸酶 P
1,RNaseP is endonuclease composed of one RNA
molecules and one protein molecules,It is a simple
RNP.
2 RNaseP are found both in prokaryotes and
eukaryotes.
3 The RNA component alone works as an
endonuclease,This RNA is a catalytic RNA,or
ribozyme.
三,Ribozyme
1 Definition,
Ribozyme is a catalytic RNA molecules that
catalyze particular biochemical reactions in
the absence of protein.
2 Examples,The self-splicing of the large subunit
of rRNA in Tetrahymena;
3 ’ G -O H H O -CCCCCCp 3 ’ G
C-O H
5 ’ p CCCCC-O H 3 ’ 5 ’ p CCCCC-O H 3 ’
G G G A G G 5 ’ G G G A G G 5 ’
C 5 与 I G S 位点附近的 RN A 5 ’ 端配对 另一轮 C 5 转移反应开始,释放 C 6
3 ’ G -O H 3 ’ G
C-O H
5 ’ p CCCCC-O H 3 ’
G G G A G G 5 ’ G G G A G G 5 ’
H O -CCCCp
G - O H 攻击 Cp C 键 C 被转移到 3 ’－ G 上； C4 被释放
图 1 3 - L -1 9 RN A 具有催化 C 6 合成的能力
The concatenmeric molecules of the RNA genome
of plant viruses are able to fold up to self-cleave
themselves into monomeric genome-sized length.
3 Application,
The minimum sequences needed for self-
cleaving are identified and applied to inhibit
gene expression by cleaving mRNA molecules,It
may be possible to
prevent virus replication,
kill cancer cells,
discover the function of new
genes by inactivating them.
茎 3
3 ’ 5 ’
剪切
C G
A U
A N
A
G N C G N N N N N
C N G N N N N N
A C
G U
N G
茎 2 A 茎 1
催化位点
图 13 － 锤头结构含 5 8 n t,有 3 个茎环和 13 碱基
的保守顺序 ( G E N E S V I F i g 3 1, 1 2 )
C
底物链 C G
A U 剪切
C G
A U
A C
A
P p p G C G C C G U C G A G C OH
O H C G C G G A G C U C G G ppp
A C
G U
U G
A
催化链
图 1 3 - 两条互补的 R N A 相互作用也可形成锤头结构
( G E N E S V I F i g 3 1, 1 2 )
