DNA- Transcription and Tranlation, RNA, Ribosomes and membrane proteins.pptxLaibaSaher
Detailed presentation on the topic of DNA, transcription and translation, RNA, Ribosomes and Membrane proteins. Along with their structure and functions. Detailed Diagram and complete description of the processes. Along with references and Gifs that makes the presentation look more creative.
DNA- Transcription and Tranlation, RNA, Ribosomes and membrane proteins.pptxLaibaSaher
Detailed presentation on the topic of DNA, transcription and translation, RNA, Ribosomes and Membrane proteins. Along with their structure and functions. Detailed Diagram and complete description of the processes. Along with references and Gifs that makes the presentation look more creative.
Transcription is the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA).Transcription is carried out by an enzyme called RNA polymerase and a number of accessory proteins called transcription factors.
For MBBS, BDS and General Biochemistry students, coding strand, sense strand, anti-sense strand, promoter, enhancers, silencers, TATA box, Goldberg Hogness box, alternative spilicing, post-transcriptional modification
Transcription and synthesis of different RNAs
Processing of RNA transcript
Catalytic RNA
RNA splicing and Spliceosome
Transport of RNA through nuclear pore
Translation and polypeptide synthesis
Posttranslational modification
Protein trafficking and degradation
Antibiotics and inhibition of protein synthesis.
1.Definition
2.Transcription is selective
3.Transcription in Prokaryotes
•Initiation
•Elongation
•RNA polymerase vs DNA polymerase
•Termination
4.Transcription in Eukaryotes
•Initiation
•Elongation
•Termination
•Post transcriptional modifications
Transcription is the process in which a gene's DNA sequence is copied (transcribed) to make an RNA molecule.
RNA polymerase is the main transcription enzyme.
Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene (directly or through helper proteins).
RNA polymerase uses one of the DNA strands (the template strand) as a template to make a new, complementary RNA molecule.
Transcription ends in a process called termination. Termination depends on sequences in the RNA, which signal that the transcript is finished.
The present ppt is covers all aspects of protein translation in bacteria as well as in eukaryotes. It also includes a brief introduction to ribosomes and tRNA which are among the key components of the translation machinery.
Transcription is the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA).Transcription is carried out by an enzyme called RNA polymerase and a number of accessory proteins called transcription factors.
For MBBS, BDS and General Biochemistry students, coding strand, sense strand, anti-sense strand, promoter, enhancers, silencers, TATA box, Goldberg Hogness box, alternative spilicing, post-transcriptional modification
Transcription and synthesis of different RNAs
Processing of RNA transcript
Catalytic RNA
RNA splicing and Spliceosome
Transport of RNA through nuclear pore
Translation and polypeptide synthesis
Posttranslational modification
Protein trafficking and degradation
Antibiotics and inhibition of protein synthesis.
1.Definition
2.Transcription is selective
3.Transcription in Prokaryotes
•Initiation
•Elongation
•RNA polymerase vs DNA polymerase
•Termination
4.Transcription in Eukaryotes
•Initiation
•Elongation
•Termination
•Post transcriptional modifications
Transcription is the process in which a gene's DNA sequence is copied (transcribed) to make an RNA molecule.
RNA polymerase is the main transcription enzyme.
Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene (directly or through helper proteins).
RNA polymerase uses one of the DNA strands (the template strand) as a template to make a new, complementary RNA molecule.
Transcription ends in a process called termination. Termination depends on sequences in the RNA, which signal that the transcript is finished.
The present ppt is covers all aspects of protein translation in bacteria as well as in eukaryotes. It also includes a brief introduction to ribosomes and tRNA which are among the key components of the translation machinery.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
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2. RNA Processing
RNA processing
2
Did you know about
RNA processing?
• Very few RNA molecules are transcribed
directly into the final mature RNA
• Most newly transcribed RNA molecules
(primary transcripts) undergo various
alterations to yield the mature product
• RNA processing is the collective term used to
describe the molecular events allowing the
primary transcript to become the mature RNA
3. Summary RNA Processing of Eukaryotic mRNA
RNA Processing
3
• Primary transcript
newly synthesized RNA
• 5’ end
Capping
5’ cap
• 3’ end
cleaved
Polyadenylation
o 80-250 adenylate residues added
Poly (A) tail
• Splicing
Introns removed
Exons joined
4. Ribosomes
RNA Processing
4
Ribosomes
Protein biosynthetic machinery
Made of 2 subunits (bacterial 30S and 50S, eukaryotes 40S and 60S)
Intact ribosome referred to as 70S ribosome in prokaryotes and 80S ribosome in
eukaryotes
In bacteria, 20.000 ribosomes/cell , 25% of cell’s mass
Mass of ribosomes is roughly 2/3 RNA
7. tRNA Processing, RNase P and Ribozymes
RNA Processing
7
1. tRNA processing in prokaryotes
2. tRNA processing in eukaryotes
3. RNase P
4. Ribozymes
tRNA 3-D structure
8. tRNA Processing
RNA Processing
8
tRNA Processing in
Prokaryotes
Mature tRNAs are generated by processing longer pre-tRNA transcrips, which
involves Spesific exo- and endonycleolytic cleavage by RNases D, E, F and P
(general) followed by base modifications which are unique to each particular
tRNA type
9. tRNA Processing
RNA Processing
9
tRNA Processing in
Prokaryotes
Primary transcripts
RNase D,E,F and P
tRNA with mature
ends
Base modifications
mature tRNAs
10. tRNA Procesing
RNA Processing
10
tRNA Processing in Eukaryotes
The pre-tRNA is synthesized with a :
1. 16 nt 5’leader
2. A 14 nt inton
3. Two extra 3’-nucleotides
11. tRNA Processing
RNA Processing
11
In Eukaryotes
1. Primary transcripts forms secondary structures recognized by
endonucleases
2. 5’leader and 3’extra nucleotide removal
3. tRNA nucleotidyl transferase adds 5’-CCA-3’to the 3’-end to
generate the mature 3’-end
4. Intron removal
12. RNase P
RNA Processing
12
RNase P
• Ribonuclease P (RNase P) is an enxyme involves in tRNA
processing that removes the 5’leader sequences from tRNA
precursors
• RNase P enzymes are found in both prokaryotes and eukaryotes,
being located in the nucleus of the latter where they are therefore
small nuclear RNPs (snRNPs)
• RNA component can catalyze pre-tRNA in vitro in the absence of
protein. This RNase P RNA is a catalytic RNA, or ribozyme
13. Ribozyme
RNA Processing
13
• Ribozymes are RNAs with catalytic activity that can catalyze particular
biochemical ractions depending on their capacity to assume particular structures
• RNase P RNA is a ribozyme
• Ribozymes function :
- During protein synthesis
- RNA processing reactions
- The regulation of gene expression
• Natural ribozymes can be classified into two different groups :
1. The self-cleaving RNAs ehich include the hammerhead, hairpin, hepatitis delta
virus, varkud satellite.
2. The self-splicing ribozymes that are the group I and II introns, RNase P
14. Ribozyme
RNA Processing
14
Self-cleaving RNA
Self-cleaving RNA encoded by viral genome to resolve the concatameric molecules
of the viral genomic RNA produced. These molecules are able to fold up in such a
way as to selfcleave themselves into monomeric.
15. 15
Hammerhead ribozyme • Virusoids, virus like elements, need another virus to
assist with replication and/or packaging (small RNAs
associated with plant RNA viruses)
• Segments of their RNA genome promote site-spesific
RNA cleavage reactions associated with replication
• Substrate RNA
Ribozyme
RNA Processing
Self-cleaving RNA
17. 17
Group I Intron Splicing
• Group I intron found in the precursor of Tetrahymena
thermophile large subunit rRNA. Group I introns have
also been found to interrupt large variety of tRNAs,
mRNAs and rRNAs in bacteria and many other
organisms.
• The Tetrahymena thermophile precursor rRNA contains
a group I intron capable of catalyzing its own excision.
Self-splicing of the intron requires presence of a
guanosine cofactor and a divalent cation, either Mg2+ or
Mn2+ and occurs via two sequential transesterification
reactions
• It can be specifically designed to repair abnormal mRNA
molecules
Ribozyme
RNA Processing
Self-splicing Introns
18. 18
Group II Intron Splicing
• Group II introns have been found in bacteria and in the
mitochondrial and chloroplast genomes of fungi, plants, and yeast
• They don’t require guanosine redisue
• Multidomain metalloenzyme
• Less widely distributed than group I
Mechanism
The 2’OH of a spesific adenosine acts as a nucleophile and
attacks the 5’ splice site creating a branched intron structure. The
3’OH of the 5’exon attacks the 3’splice site. Ligating the exons and
releasing the intron as a lariant structure
Ribozyme
RNA Processing
Self-splicing Introns
19. Ribozyme
RNA Processing
19
Ribozymes can be used as therapeutic agents in :
1. Correcting mutant mRNA in human cells
2. Inhibiting unwanted gene expression
- Kill cancer cells
- Prevent virus replication
22. mRNA PROCESSING, hnRNPs AND snRNPs
RNA Processing
22
Processing of mRNA
hnRNP
snRNP particles
5’capping
3’ cleavage and polyadenylation
Splicing
Pre-mRNA Methylation
23. Processing of mRNA
RNA Processing
23
• There is essentially no processing of prokaryotic mRNA, it can start to be
translated before it has finished being transcribed.
• Prokaryotic mRNA is degraded rapidly from the 5’ end
• In eukaryotes, mRNA is synthesized by RNA Pol II as longer precursors (pre-mRNA),
the population of different RNA Pol II transcripts are called heterogeneous nuclear
RNA (hnRNA). Among hnRNA, those processed to give mature mRNAs are called
pre-mRNAs. Pre-mRNA molecules are processed to mature mRNAs by 5’-capping,
3’-cleavage and polyadenylation, splicing and methylation.
25. hnRNP: hnRNA + proteins
RNA Processing
25
• The hnRNA synthesized by RNA Pol II is mainly pre-mRNA and
rapidly becomes covered in proteins to form heterogeneous
nuclear ribonucleoprotein (hnRNP)
• The hnRNP proteins are though to help keep the hnRNA in a
single-stranded form and to assist in the various RNA
processing reactions
26. snRNP particles: snRNA + proteins
RNA Processing
26
1. snRNAs are rich in the base uracil, which complex with
specific proteins to form snRNPs.
2. The most abundant snRNP are involved in pre-mRNA splicing,
U1,U2,U4,U5 and U6.
3. A large number of snRNP define methylation sites in pre-rRNA.
27. snRNP particles
RNA Processing
27
• They are synthesized in the nucleus by RNA Pol II and have a
normal 5’-cap.
• They are exported to the cytoplasm where they associate with
the common core proteins and with other specific proteins.
• Their 5’-cap gains two methyl groups and they are then
imported back into the nucleus where they function in splicing.
30. Capping
RNA Processing
30
Most eukaryotic mRNAs have 5’cap
7-methylguanosine linked to the 5’-terminal residue
5’-5’ triphosphate bridge
A cap may be O2 methylated
At the transcripts leading nucleoside, cap-1
- Predominant cap in multicellular organisms
At the first two nucleosides, cap-2
At neither, cap-0
- The predominant cap in unicellular
eukaryotes
Has role in translation
Initiation
31. Steps in Capping
RNA Processing
31
Cap added when transcript is about 30
nucleotides long
1.Removal of the leading phosphate group
from the mRNA’s 5’ terminal triphosphate
group
- Phoshydrolase (also called RNA
triphosphatase)
2. Capping enzyme
- A guanylytransferase
32. Steps in Capping
RNA Processing
32
3. Methylation of guanine
Guanosine-7-methyltransferase
- Uses S-adenosylmethionine (SAM or
adoMet) product is S-
adenosylhomocysteine (adoHcy)
4. 2’-O-methyltransferase
SAM (cap-1, cap-2, cap-3)
Both the capping enzyme and guanosine-7-
methyltransferase bind to RNA-Pol II’S
phosphorylated CTD (c-terminal domain)
33.
34. Function of capping
RNA Processing
34
1.Protection from degradation
2.Increasing translational efficiency
3.Transport to cytoplasm
4.Splicing of first exon
36. Cleavage and Polyadenylation
RNA Processing
36
• In most pre-mRNAs, the mature 3’-end of the molecule is generated by
cleavage followed by the addition of a run, or tail, of A residues which is
called the poly(A) tail.
• RNA polymerase II does not usually terminate at distinct site
• Pre-mRNA is cleaved ~20 nucleotides downstream of polyadenylation
signal (AAUAAA)
• ~250 AMPs are then added to the 3´ end
• Almost all mRNAs have poly(A) tail
37. Cleavage and Polyadenylation
RNA Processing
37
Mechanism
• Poly (A) tails added to primary transcripts of mRNA
- Eukaryotic mRNA invariably mono-cistronic
1. Transcript extends beyond site of poly (A) addition
- Large complex binds
- Endonuclease component cleaves 15 to 25
nucleotides on 3’ side of
- AAUAAA
2. Poly(A) Polymerase (PAP)
- No template
- Needs a primer
- Adds 80-250 A
38. Cleavage and Polyadenylation
RNA Processing
38
Function
• Increasing mRNA stability
• Increasing translational efficiency
• Splicing of last intron
41. Splicing
RNA Processing
41
• the process of cutting the pre-mRNA to remove the introns and
joining together of the exons is called splicing.
• it takes place in the nucleus before the mature mRNA can be
exported to the cytoplasm.
• Splicing requires a set of specific sequences to be present. The 5’-
end of almost all introns has the sequence 5’-GU-3’ and the 3’-end is
usually 5’-AG-3’. The AG at the 3’-end is preceded by a pyrimidine-
rich sequence called the polypyrimidine tract
43. Splicing
RNA Processing
43
Exons are the coding sequences that appear on split genes and
primary transcripts, and will be expressed to matured mRNA
Introns are the non-coding sequences that are transcripted into
primary mRNAs, and will be cleaved out in the later splicing process
Exons and Introns
44. Splicing
RNA Processing
44
• Catalyzes pre-mRNA splicing in nucleus
• Composed of five small nuclear RNAs (snRNAs) and associated
proteins (snRNPs) assembled on the pre-mRNA
• Splicing reaction is catalyzed by RNA
Spliceosome
48. Alternative mRNA Processing
RNA Processing
48
Alternative
Processing
• Alternative mRNA processing is the
conversion of pre-mRNA species into
more than one type of mature mRNA.
• Types of alternative RNA processing
include alternative (or differential) splicing
and alternative (or differential) poly(A)
processing.
49. Alternative mRNA Processing
RNA Processing
49
Alternative
Poly(A) Sites
• Some pre-mRNAs contain more than one
poly(A) site and these may be used under
different circumstances to generate
different mature mRNAs.
• In one cell the stronger poly(A) site is
used by default, but in other cell a factor
may prevent stronger site from being used.
50. Alternative Poly(A) Sites
RNA Processing
50
• Thyroid
- First Poly(A) site
- Exon 4 retained
- Produces : calcitonin
• Brain
- Second poly(A) site
- Exon 4 spliced out
- Produces : CGRP,
calcitonin-gene-related
peptide
51. Alternative mRNA Processing
RNA Processing
51
Alternative Splicing
The generation of different mature mRNAs
from a particular type of gene transcript can
occur by varying the use of 5’-and3’-splice sites
in four ways :
a) By using different promoters
b) By using different poly(A) sites
c) By retaining certain introns
d) By retaining or removing certain exons
