1. Eukaryotic pre-mRNA undergoes processing after being exported from the nucleus which involves removal of introns, addition of a 5' cap, and 3' polyadenylated tail to produce mature mRNA.
2. The mature mRNA is translated by ribosomes in the cytoplasm. Some viruses utilize cap-independent translation initiation or other mechanisms like leaky scanning, frameshifting, or suppression of termination to express their genes.
3. Interferons induce antiviral responses including RNase L and PKR activation. Viruses have evolved strategies to antagonize PKR such as inhibiting its dsRNA binding, dimerization, or kinase activity to prevent host translation shutoff.
description of mechanism of transcription in prokaryotes and eukaryotes with clear explanation and clear pictures and also mentiong of different promotors and enhancers and silencers
Eukaryotic transcription is the elaborate process that eukaryotic cells use to copy genetic information stored in DNA into units of transportable complementary RNA replica.
This presentation is about the transcription machinery that is required for the transcription in eukaryotes. The comparison between the transcription factors involved in prokaryotes and eukaryotes. The initiation of transcription and how it helps in producing a mRNA.
description of mechanism of transcription in prokaryotes and eukaryotes with clear explanation and clear pictures and also mentiong of different promotors and enhancers and silencers
Eukaryotic transcription is the elaborate process that eukaryotic cells use to copy genetic information stored in DNA into units of transportable complementary RNA replica.
This presentation is about the transcription machinery that is required for the transcription in eukaryotes. The comparison between the transcription factors involved in prokaryotes and eukaryotes. The initiation of transcription and how it helps in producing a mRNA.
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 in eukariotes by kk sahuKAUSHAL SAHU
INTRODUCTION
A STRUCTURAL GENE
EUKARYOTIC RNAPs
MACHANISM OF TRANSCRIPTION IN EUKARYOTES:
- INITIATION
-ELONGATION
-TERMINATION
RNA SPLISING
DIFFERENT BETWEEN PROKARYOTIC & EUKARYOTIC TRANSCRIPTION
BIBLIOGRAPHY
The process of transcription is the first stage of gene expression resulting in the production of a primary RNA transcript from the DNA of a particular gene.
This step of gene expression which is followed by a number of post-transcriptional processes such as RNA splicing and translation.
These lead ultimately to the production of a functional protein and this process is highly regulated.
Both basal transcription and its regulation are dependent upon specific protein factors known as transcription factors.
These highly specific protein bind to the specific regulatory gene of DNA sequence and control the transcription process and regulate it.
For example- enzyme RNA polymerase catalyzes the chemical reaction that synthesize RNA, using the DNA gene as a template, the transcription factor control when, where, and how efficiency RNA polymerase function.
Play an important role in the normal development and routine of cellular function.
Basics of Undergraduate/university fellows
Transcription is more complicated in eukaryotes than in prokaryotes because
eukaryotes possess three different classes of RNA polymerases and because of the
way in which transcripts are processed to their functional forms.
More proteins and transcription factors are involved in eukaryotic transcription.
The process of synthesis of protein from the mRNA (messenger RNA) is called as "TRANSLATION". In this slide you will see the introduction, stages, factors, and requirements for this process. It also includes a visual description of the process "TRANSLATION" that will easily explain the process by animation.
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 in eukariotes by kk sahuKAUSHAL SAHU
INTRODUCTION
A STRUCTURAL GENE
EUKARYOTIC RNAPs
MACHANISM OF TRANSCRIPTION IN EUKARYOTES:
- INITIATION
-ELONGATION
-TERMINATION
RNA SPLISING
DIFFERENT BETWEEN PROKARYOTIC & EUKARYOTIC TRANSCRIPTION
BIBLIOGRAPHY
The process of transcription is the first stage of gene expression resulting in the production of a primary RNA transcript from the DNA of a particular gene.
This step of gene expression which is followed by a number of post-transcriptional processes such as RNA splicing and translation.
These lead ultimately to the production of a functional protein and this process is highly regulated.
Both basal transcription and its regulation are dependent upon specific protein factors known as transcription factors.
These highly specific protein bind to the specific regulatory gene of DNA sequence and control the transcription process and regulate it.
For example- enzyme RNA polymerase catalyzes the chemical reaction that synthesize RNA, using the DNA gene as a template, the transcription factor control when, where, and how efficiency RNA polymerase function.
Play an important role in the normal development and routine of cellular function.
Basics of Undergraduate/university fellows
Transcription is more complicated in eukaryotes than in prokaryotes because
eukaryotes possess three different classes of RNA polymerases and because of the
way in which transcripts are processed to their functional forms.
More proteins and transcription factors are involved in eukaryotic transcription.
The process of synthesis of protein from the mRNA (messenger RNA) is called as "TRANSLATION". In this slide you will see the introduction, stages, factors, and requirements for this process. It also includes a visual description of the process "TRANSLATION" that will easily explain the process by animation.
This is a mini-research work presented in partial fulfilment of the requirements for the award of a masters degree in Biochemistry, University of Ibadan.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
The Indian economy is classified into different sectors to simplify the analysis and understanding of economic activities. For Class 10, it's essential to grasp the sectors of the Indian economy, understand their characteristics, and recognize their importance. This guide will provide detailed notes on the Sectors of the Indian Economy Class 10, using specific long-tail keywords to enhance comprehension.
For more information, visit-www.vavaclasses.com
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
How to Create Map Views in the Odoo 17 ERPCeline George
The map views are useful for providing a geographical representation of data. They allow users to visualize and analyze the data in a more intuitive manner.
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
The Art Pastor's Guide to Sabbath | Steve ThomasonSteve Thomason
What is the purpose of the Sabbath Law in the Torah. It is interesting to compare how the context of the law shifts from Exodus to Deuteronomy. Who gets to rest, and why?
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
4. Processing of eukaryotic mRNA
• RNA processing achieves three things:
1) Removal of Introns
2) Addition of a 5’ cap
3) Addition of a 3’ tail
The mRNA then moves out of the nucleus and is translated in the
cytoplasm.
3’ Poly A Tail
Protein Coding Region
3’ UTR5’ UTR
G
5’ Cap
Exon 2 Exon 3Exon 1 AAAAA
4
6. Model of eukaryotic ribosome
• rRNAs are believed to play a catalytic role in protein
synthesis.
• After removal of 95% of the ribosomal proteins, the
60S subunit can catalyze formation of peptide bonds.
• Ribosomal proteins are now believed to help fold the
rRNAs properly and to position the tRNAs.
6
7. •Small & large ribosomal
subunits.
•A Binding site for
the mRNA is present on
small subunit.
•Two binding sites
(P & A) bind tRNAs on
large subunit.
•P site – holds the tRNA
carrying the growing
polypeptide chain.
•A site – holds the tRNA with
the next AA to be added.
• Ribosomes hold the
mRNA and tRNAs together
and connect the amino
acids at the A site to the
growing polypeptide.
Ribosome Structure 7
8. Structure of tRNA
• Aligns each amino acid with
the corresponding codon
• 70-80 nt long
• 3’ end has the 5’- CCA
sequence to which aa are
linked
• The opposite end contains
the anticodon loop
• Contains modified bases
8
9. Many RNA Viruses have
capped genomic RNAs similar
to eukaryotic host mRNAs
• Most eukaryotic mRNAs are capped at
the 5’ end during nuclear processing.
• The terminal 5’ phosphate is first
removed by a 5’ triphosphatase.
• Guanyltransferase transfers GMP from
GTP to the 5’ end of the mRNA to add
the GpppN cap structure.
• The 5’ terminal inverted G residue is
then modified by methylation.
• Many RNA viruses replicate in the
cytoplasm and must use a viral
dependent capping mechanism
supplied by the RNA-Dependent-RNA
Polymerase.
• The Cap structure, m7GpppN, is most
common in viral and mammalian
mRNAs.
9
10. Three distinct stages of translation
Initiation
•Rate limiting step
•Requires hydrolysis of ATP and GTP
•Results in formation of a complex containing the
mRNA, the ribosome and the initiator Met-tRNA
A. 5’ end (Cap) dependent initiation
• The initiation complex binds to the 5’ cap
structure and scans in a 5’ to 3’ direction until
initiating AUG is encountered
B. Internal ribosome entry
• Initiation complex binds upstream of initiation
codon
10
11. • The first step is the recognition of the 5’ cap by eIF4F, which consists of three
proteins, eIF4E, eIF4G and eIF4A.
• Cap binding protein, eIF4E, binds to cap
• The N-terminus of eIF4G binds eIF4E and the C-terminus binds eIF4A
• The 40S subunit binds to eIF4G via eIF3
5’ end (cap) dependent initiation: 11
12. The 40S complex then scans
down the 5’ untranslated region
to the first AUG codon.
A GTP hydrolysis step by eIF5
triggers GDP binding of eIF2
and release of initiation
proteins.
The 60S subunit joins the
complex and the 80S
ribosome initiates translate
the ORF.
An initiation complex forms at
the cap with the 40S ribosomal
subunit and other translation
initiation factors.
Cap-Dependent Initiation of Protein Synthesis in Eukaryotes12
13. Ribosome selects
aminoacylated tRNA
eEF1a and GTP are bound to
aminoacylated tRNA
Ribosome catalyzes formation
of a peptide bond
Translocation is dependent on
eEF2 and GTP hydrolysis
Many ribosomes may translate
mRNAs simultaneously on the
same strand.
Elongation
P A
eEF1a
eEF2
GTP
GTP
13
14. Termination
•Translation is terminated
at one of three stop codons
(UAA, UAG & UGA).
• Termination codon at the
A site is recognized by the
release factor instead of a
tRNA
• The release factor binds
the termination codon
• The peptide chain is then
released followed by
dissociation of the tRNA
and the ribosome
14
15. • The 5’ end dependent initiation is stimulated by the poly(A) binding protein
Pabp1p, which interacts with eIF4G
• This interaction circularizes the mRNA and facilitates formation of the
initiation complex
• Mechanism to ensure that only intact mRNA is translated
Closed loop model:
15
16. • mRNAs of picornaviruses lack 5’ cap
• Ribosomes bind internally rather than at the mRNA 5’ end
• 5’ end of poliovirus RNA promotes internal binding of 40S subunit at
internal ribosome entry site (IRES)
• In poliovirus infected cells eIF4G is cleaved, inactivating translation
of cellular mRNAs
•The initiation in the IRES does not depend on the presence of a cap
structure, but requires C-terminal fragment of eIF4G to recruit the 40S
subunit through interaction with eIF3.
5’end (cap) independent initiation:
Poliovirus
16
17. Five different types of IRES sequences are found on viral RNAs:
Type I-entero and rhinoviruses (poliovirus)
Initiation codon is located past the 3’ end of the IRES
40S binds to IRES scans to AUG
Type II-cardio and apthoviruses (EMCV)
Initiation codon is at the 3’ end of the IRES
40S binds at or near AUG no scanning occurs
Type III- hepatitis A virus
initiation codon is located past the 3’ end of the IRES
requires all of initiation proteins, including eIF4E
Type IV- hepatitis C virus
The 3’ end of the hepatitis C virus IRES extends
beyond the AUG codon
Type V-cricket paralysis virus
IRES ends at the initiation codon, although it is not an AUG
codon, no initiation factors are required
initiation codon is placed at the A site instead of the P
site
17
19. Hepatitis C virus IRES:
• 40S ribosomal subunit binds directly to Hepatitis C virus IRES in the
absence of most initiation factors
• A dramatic change in the conformation of the 40S subunit occurs when it
binds Hepatitis C virus IRES setting the AUG at the P site
• eIF3 also binds to the Hepatitis C virus IRES
19
21. Viral translation strategies
Polyprotein synthesis
Picornaviruses- Entire (+) sense RNA genome is translated into a single
large polyprotein. Processing is carried out by two virus encoded
proteases 2A pro and 3C pro.
Flaviviruses- Viral precursor proteins are processed by cellular proteases.
The (+) sense RNA genome is translated into a polyprotein precursor
processed by viral serine protease and by host signal peptidase.
Potyvirus group of plant viruses- Potato virus Y and tobacco etch virus
contain a (+) sense genome RNA of around 10,000 bases which has a
single open reading frame. This polyprotein is processed by viral
encoded proteases.
21
23. Leaky scanning
Although majority of eukaryotic mRNAs are monocistronic, some viral
mRNAs encode overlapping reading frames. The first start site is in a
poor context, some ribosomes can bypass it and initiate at the second
AUG, which has a better context. This will result in translation of two
different proteins.
23
24. Reinitiation
Rare in eukaryotes, but very common in prokaryotic cellular and viral
mRNAs. Some eukaryotic mRNAs contain upstream AUG codons that
terminate before the downstream reading frame. The upstream open
reading frames may be translated, with reinitiation occurring at the
downstream open reading frame.
24
25. In influenza B virus mRNA, M2 initiation codon is part of the termination
codon for M1 protein. M2 synthesis is not efficient and dependent on M1
synthesis
Reinitiation of translation in influenza B virus
25
26. Suppression of termination
Suppression of termination occurs during translation of may viral
mRNAs as a means of generating a second protein with extended
carboxy terminus. In retroviruses, gag and pol genes are encoded by a
single mRNA and separated by an amber termination codon UAG.
Translational suppression of the amber codon allows synthesis of the
gag pol precursor.
A similar strategy is used by tobacco mosaic virus to translate its
replicase proteins.
Translation suppression is mediated by suppressor tRNAs that can
recognize termination codons and insert a specific amino acid. The
nucleotide sequence 3’ of the termination codon also plays an important
role in the efficiency of translational suppression.
26
28. Ribosomal frameshifting
Ribosomal frameshifting is a process in which ribosomes move to a
different reading frame and continue translation in that reading frame.
It was discovered in cells infected with Rous sarcoma virus and has
since been described for many other viruses including other
retroviruses, (+) strand RNA viruses and herpes simplex virus.
Requires a “slippery” sequence X-XXY-YYZ (in Rous sarcoma virus A-
AAU-UUA) and an RNA secondary structure called a pseudoknot five to
eight nucleotides downstream.
Two tRNAs in the zero reading frame slip back by one nucleotide to the
–1 phase and each tRNA base pairs with the mRNA in the first two
nucleotides of each codon.
As a result of the frameshift a Gag-pol fusion is produced at about 5% of
the level of Gag protein.
28
30. REGULATION OF TRANSLATION DURING VIRAL INFECTION
Interferons are produced in response to viral infection as part of the
rapid innate immune response
Interferons bind to cell surface receptors and activate transcription of
antiviral genes
Two interferon induced genes encode RNase L and protein kinase
RNA-activated (Pkr)
RNase L degrades RNA
Pkr phosphorylates eIF2a, inhibiting translation initiation
Pkr is a serine threonine kinase composed of an N-terminal regulatory
domain and a C-terminal catalytic domain
Pkr is activated by the binding of dsRNA to two dsRNA binding motifs
at the N-terminus of the protein.
30
32. Viral regulation of Pkr
Viruses use at least five different mechanisms to block Pkr activation
or to stop activated Pkr from inhibiting translation
• inhibition of dsRNA binding-
adenovirus VA RNA binds Pkr blocks its activation by dsRNA
• vaccinia virus E3L protein sequesters ds RNA
• inhibition of Pkr dimerization
influenza virus P58
hepatitis C virus NS5A
• inhibitors of kinase function-
vaccinia virus K3L protein has homology to N- terminus
of eIF2-a
32