清华大学：《分子生物学》课程PPT教学课件（基因ene）第五章 信使RNA（Messenger RNA）

Chapter 5 Messenger RNA 清苇大当

Chapter 5 Messenger RNA

5.1 Introduction 5.2 Transfer RNA is the adapter 5.3 Messenger RNA is translated by ribosomes 5.4 The life cycle of bacterial messenger RNA 5.5 Translation of eukaryotic mRNA 5.6 The 5'end of eukaryotic mRNA is capped 5.7 The 3'terminus is polyadenylated 5.8 Bacterial mRNA degradation involves multiple enzymes 5.9 mRNA degradation involves multiple activities 5.10 Sequence elements may destabilize mRNA 5.11 Nonsense mutations trigger a surveillance system 清苇大当

5.1 Introduction 5.2 Transfer RNA is the adapter 5.3 Messenger RNA is translated by ribosomes 5.4 The life cycle of bacterial messenger RNA 5.5 Translation of eukaryotic mRNA 5.6 The 5 end of eukaryotic mRNA is capped 5.7 The 3 terminus is polyadenylated 5.8 Bacterial mRNA degradation involves multiple enzymes 5.9 mRNA degradation involves multiple activities 5.10 Sequence elements may destabilize mRNA 5.11 Nonsense mutations trigger a surveillance system

5.1 Introduction Coding region is a part of the gene that represents a protein sequence Coding strand of DNA has the same sequence as mRNA. template strand of double-stranded DNA is the one that is used to specify the sequence of a complementary single strand of RNA.(The non-template strand is identical in sequence to the RNA product. Transcription is synthesis of RNA on a DNA template. Translation is synthesis of protein on the mRNA template. 情華大当

Coding region is a part of the gene that represents a protein sequence. Coding strand of DNA has the same sequence as mRNA. template strand of double-stranded DNA is the one that is used to specify the sequence of a complementary single strand of RNA. (The non-template strand is identical in sequence to the RNA product.) Transcription is synthesis of RNA on a DNA template. Translation is synthesis of protein on the mRNA template. 5.1 Introduction

Coding strand sense 5.1 Introduction Figure 5.1 Transcription Template strand antisens e generates an RNA which is complementary to the DNA Transc ription template strand and has the same sequence as the DNA coding strand.Translation reads each triplet of bases into one amino acid.Three Translation turns of the DNA double helix contain 30 bp,which cide for 10 amino acids 清菜大当

Figure 5.1 Transcription generates an RNA which is complementary to the DNA template strand and has the same sequence as the DNA coding strand. Translation reads each triplet of bases into one amino acid. Three turns of the DNA double helix contain 30 bp, which cide for 10 amino acids. 5.1 Introduction

5.2 Transfer RNA is the adapter Aminoacyl-tRNA is transfer RNA carrying an amino acid;the covalent linkage is between the NH2 group of the amino acid and either the 3'- or 2'-OH group of the terminal base of the tRNA. Aminoacyl-tRNA synthetases are enzymes responsible for covalently linking amino acids to the 2'-or 3'-OH position of tRNA. Anticodon is a trinucleotide sequence in tRNA which is complementary to the codon in mRNA and enables the tRNA to place the appropriate amino acid in response to the codon. Loop is a single-stranded region at the end of a hairpin in RNA (or single-stranded DNA);corresponds to the sequence between inverted repeats in duplex DNA. Stem is the base-paired segment of a hairpin 情苇大兰

Aminoacyl-tRNA is transfer RNA carrying an amino acid; the covalent linkage is between the NH2 group of the amino acid and either the 3′- or 2′-OH group of the terminal base of the tRNA. Aminoacyl-tRNA synthetases are enzymes responsible for covalently linking amino acids to the 2′- or 3′-OH position of tRNA. Anticodon is a trinucleotide sequence in tRNA which is complementary to the codon in mRNA and enables the tRNA to place the appropriate amino acid in response to the codon. Loop is a single-stranded region at the end of a hairpin in RNA (or single-stranded DNA); corresponds to the sequence between inverted repeats in duplex DNA. Stem is the base-paired segment of a hairpin. 5.2 Transfer RNA is the adapter

NH2 R 5.2 Transfer RNA C-H Amino acid Amino acid linked 0 to 3 end of tRNA is the adapter 0 CH2 Figure 5.2 A tRNA has the Amino dual properties of an adaptor that recognizes 51 both the amino acid and Arm consists of codon.The 3 adenosine Base-paired stem is covalently linked to an IIIr农 amino acid.The anticodon base pairs with the codon Single- on mRNA. stranded loop 2 Anticodon- codon pairing 清苇大当 NNNNNNN mRNA

Figure 5.2 A tRNA has the dual properties of an adaptor that recognizes both the amino acid and codon. The 3 adenosine is covalently linked to an amino acid. The anticodon base pairs with the codon on mRNA. 5.2 Transfer RNA is the adapter

5.2 Transfer RNA is the adapter Acceptor arm D am 23456 ACC13210知85 TyC arm U*7 Py59 Figure 5.3 The tRNA 16Pu 1 9 65646362 1312Py1 95051520 Pu G cloverleaf has G208 2223Pu2 Py 2 7 invariant and semi- 27.49444546 28- invariant bases,and a 30 40 Extra arm conserved set of base 38 pairing interactions. 56r Anticodon 情菜大当

Figure 5.3 The tRNA cloverleaf has invariant and semi￾invariant bases, and a conserved set of base pairing interactions. 5.2 Transfer RNA is the adapter

Clover leaf secondary structure has four arms 3 5.2 Transfer RNA Amino acid stem D arm Tyc arm is the adapter Anticodon arm 2D projection has 2 perpendicular duplex regions Figure 5.4 Transfer RNA folds into a compact L-shaped Backbone follows L-shaped structure tertiary structure with Amino acid the amino acid at one NH end and the anticodon at Tyc arm Amino acid stem the other end D am Anticodon arm 清苇大当 Anticodon

Figure 5.4 Transfer RNA folds into a compact L-shaped tertiary structure with the amino acid at one end and the anticodon at the other end. 5.2 Transfer RNA is the adapter

5.2 Transfer RNA is the adapter Figure 5.5 A space-filling model shows that tRNAPhe tertiary structure is compact.The two views of tRNA are rotated by 900 Photograph kindly provided by S.H.Kim 情華大当

Figure 5.5 A space-filling model shows that tRNAPhe tertiary structure is compact. The two views of tRNA are rotated by 90o . Photograph kindly provided by S. H. Kim. 5.2 Transfer RNA is the adapter

5.2 Transfer RNA is the adapter SH D.esulfuration CH,Cysteine changes CHa Alanine amino acid MH NH2 68 Codon recognition unchanged 06& Figure 5.6 The meaning of tRNA is determined by its anticodon and not by its amino acid 清苇大当

Figure 5.6 The meaning of tRNA is determined by its anticodon and not by its amino acid. 5.2 Transfer RNA is the adapter