Copyright@The McGraw-Hill Companies,Inc.Permission required for reproduction or display. Chapter 16 Other RNA Processing Events
Chapter 16 Other RNA Processing Events
16.1 Ribosomal RNA processing Eukaryotes .Structure of rRNA genes .The rRNA genes in eukaryotes are repeated several hundred times and clustered together in the nucleolus of the cell. .The rRNA genes are separated by regions called nontranscribed spacers (NTSs). ·rRNA processing .The trimming of excess regions from an RNA precursor is called processing. RNA processing similar to splicing,but it duffers from splicing in that no RNAs are stitched together during processing
16.1 Ribosomal RNA processing Eukaryotes •Structure of rRNA genes •The rRNA genes in eukaryotes are repeated several hundred times and clustered together in the nucleolus of the cell. •The rRNA genes are separated by regions called nontranscribed spacers (NTSs). •rRNA processing •The trimming of excess regions from an RNA precursor is called processing. • RNA processing similar to splicing, but it duffers from splicing in that no RNAs are stitched together during processing
The structure of rRNA gene Figure 16.1a rRNA gene NTS rRNA gene NTS Nontranscribed spacers
The structure of rRNA gene Nontranscribed spacers
Processing scheme of 45S human (HeLa)rRNA precursor rRNA gene RNA pol.I NTS 5 18S 5.8S 28S the 5'-end of the 45S precursor 45S RNA is removed→ Step1 441 S precursor▣ 18S 5.8S 28S is cut into two parts 41S Take place Step 2. in the 32S precursor 20S precursor nucleolus 18S ☐5.8S 28S 20S 32S 3'-end is removed Step 3. Step 4. cut 18S 5.8 28S rRNAs are made and the 5.8S and 28S rRNAs Step 5. associated by base pairing ribosome 5.8S Figure 16.2 M assembled 28S
rRNA gene Processing scheme of 45S human (HeLa) rRNA precursor RNA pol. I NTS Take place in the nucleolus rRNAs are made and ribosome assembled the 5.8S and 28S rRNAs associated by base pairing the 5'-end of the 45S precursor RNA is removed→ 32S precursor 3’-end is removed is cut into two parts 20S precursor 41S precursor cut
The evidence for this sequence of events a pulse-chase procedure to establish a precursor-product relationship between the 45S precursor and the 28S and 18S mature rRNAs Culture cell 3H]uridine short-lived Incubation with intermediate pulse-chase isotopes for a short time (pulse) 18S and 28S rRNAs increase Chase with 45S precursol decreased cold ubstrates The labeled RNA sedimented as a broad peak Collect samples centered at about 45S.Then he "chased"the label and detection at in this RNA into 18S and 28S rRNAs different time One or more RNA species was a precursor to 18S course. and 28S rRNAs
The evidence for this sequence of events a pulse-chase procedure to establish a precursor-product relationship between the 45S precursor and the 28S and 18S mature rRNAs. Culture cell Incubation with isotopes for a short time (pulse) Collect samples and detection at different time course. The labeled RNA sedimented as a broad peak centered at about 45S. Then he “chased" the label in this RNA into 18S and 28S rRNAs One or more RNA species was a precursor to 18S and 28S rRNAs Chase with cold ubstrates pulse-chase [ 3H]uridine 45S precursol decreased 18S and 28S rRNAs increased short-lived intermediates
Isolation of 45S rRNA-processing intermediates from poliovirus(脊髓灰质炎病毒)-infected HeLa cells Culture cell virus-infected 5000 2000 Incubation with 32S ←-28S isotopes for a 45S short time (pulseoo 1500 n 1 Chase with 母 6 1000 cold 9 0 02000 substrates 20S 中 24 500 Collect samples 1000 and detection at different time 5.0B8888888808 Figure 16.3 0 60 80 100 120 course. Slice number >what intermediates are?How long of its half- lift
Isolation of 45S rRNA—processing intermediates from poliovirus(脊髓灰质炎病毒)-infected HeLa cells Culture cell Incubation with isotopes for a short time (pulse) Collect samples and detection at different time course. ➔ what intermediates are? How long of its halflift ? Chase with cold substrates virus-infected
The rRNA-processing steps are managed in the nucleolus by a class of small nucleolar RNAs (snoRNAs),associated with many proteins in small nucleolar ribonucleoproteins(snoRNPs). There are many hundreds of snoRNAs,but just a few of them participate in rRNA processing.In particular, three snoRNPs (E1.E2,and E3)have been shown to interact with distinct regions in pre-rRNA
The rRNA—processing steps are managed in the nucleolus by a class of small nucleolar RNAs (snoRNAs)，associated with many proteins in small nucleolar ribonucleoproteins(snoRNPs). There are many hundreds of snoRNAs，but just a few of them participate in rRNA processing. In particular， three snoRNPs (E1．E2，and E3) have been shown to interact with distinct regions in pre—rRNA．
小结 核糖体RNA在真核生物细胞核中以前体的形式形成，这 些前体必须被加工才能释放出成熟的rRNAS。 虽然成熟RNA的准确大小在不同物种之间是不同的，但 在所有的真核生物中，前体RNAs的顺序都是18S,5.8S, 28S。在人的细胞中前体是45S,并在加工过程产生41S, 32S和20S的中间产物形式。 snoRNAs在这些加工的过程中起了重要的作用
小结 核糖体RNA在真核生物细胞核中以前体的形式形成，这 些前体必须被加工才能释放出成熟的rRNAs。 虽然成熟rRNA的准确大小在不同物种之间是不同的，但 在所有的真核生物中，前体RNAs的顺序都是18S，5.8S， 28S。在人的细胞中前体是45S，并在加工过程产生41S， 32S和20S的中间产物形式。 snoRNAs在这些加工的过程中起了重要的作用
Prokaryotes ·rrn operons .The bacterium have several rrn operons that contain rRNA genes. rrnD operon 16S 23S 5S tRNA ERNA tRNA Transcription of the rrnD operon yields a 30s precursor,which must be cut up to release the three rRNA and three tRNAs. rRNA processing
Prokaryotes • rrn operons •The bacterium have several rrn operons that contain rRNA genes. tRNA tRNA tRNA Transcription of the rrnD operon yields a 30S precursor, which must be cut up to release the three rRNA and three tRNAs. rRNA processing
rrnD operon 23S rRNA 16S 23S 5S U U Transcription U A 30s precursor Q A A U G complementary Processing(including RNase Ill) A RNase lll- G G RNase Ill U Figurel6.4 RNase E remoy the 5S rRNA from the precursor
30S precursor complementary RNase E remov the 5S rRNA from the precursor Figure16.4