Control of Gene Expression | Transcription Factors, Enhancers, Promotor, Acetylation vs Methylation

Summary

This video from Medicosis PerfectS explains gene expression regulation in eukaryotes, covering enhancers, promoters, transcription factors, and chromatin modifications. The video highlights key differences between euchromatin (open, active DNA) and heterochromatin (closed, inactive DNA), as well as the roles of acetylation and methylation. It also dives into RNA processing, post-transcriptional and post-translational modifications, and the central dogma of molecular biology. The content further discusses how transcription factors and enhancers regulate transcription and gene expression, emphasizing the biochemical processes involved. The video offers a clear, structured approach to understanding biochemistry.

Takeaways

• 🧬 The script discusses DNA replication, transcription, and translation, including the central dogma of molecular biology.
• 🧩 Exons are expressed, while introns are spliced out and discarded during RNA processing.
• 🧪 RNA polymerase has different types: RNA polymerase 1 synthesizes rRNA, RNA polymerase 2 synthesizes mRNA, and RNA polymerase 3 synthesizes tRNA.
• 🧫 mRNA undergoes post-transcriptional modifications, including splicing, adding a 5' cap, and a 3' poly-A tail.
• 🧠 Chromatin can be in two forms: euchromatin (loose and active for transcription) and heterochromatin (dense and inactive).
• 🔬 Enhancers are regulatory elements that are located far from the promoter and help boost transcription, while promoters are located near the start of genes.
• ⚡ Transcription factors assist in assembling the transcription machinery and bind to promoters to stimulate or inhibit transcription.
• 💡 Acetylation of histones activates transcription, while methylation of DNA silences genes by making chromatin more condensed.
• 🧬 Cortisol and other hormones can influence gene expression by binding to specific hormone response elements in DNA.
• 📚 Quiz example: Histone deacetylation leads to gene inactivation, turning euchromatin into heterochromatin, making the DNA inaccessible for transcription.

Q & A

What is the central dogma of molecular biology?

The central dogma of molecular biology explains how genetic information flows in a biological system. It involves the processes of replication (copying DNA), transcription (converting DNA into RNA), and translation (converting RNA into proteins).

What are the main differences between DNA and RNA?

DNA is double-stranded and contains deoxyribose sugar, while RNA is single-stranded and contains ribose sugar. DNA has thymine (T), whereas RNA has uracil (U) instead of thymine.

What are nucleosides and nucleotides, and how do they differ?

A nucleoside consists of a nitrogenous base and a sugar molecule, while a nucleotide has a nitrogenous base, sugar, and one or more phosphate groups.

What is the role of RNA polymerase in transcription?

RNA polymerase is the enzyme responsible for converting DNA into RNA. RNA polymerase I produces rRNA, RNA polymerase II produces mRNA, and RNA polymerase III produces tRNA.

What happens during post-transcriptional modification?

Post-transcriptional modifications involve splicing out introns (non-coding regions), adding a 5' cap, and a poly-A tail at the 3' end. These changes convert the initial hnRNA (heterogeneous nuclear RNA) into mature mRNA.

What are transcription factors and enhancers, and how do they influence transcription?

Transcription factors are proteins that bind to specific DNA sequences (promoters) to initiate or regulate transcription. Enhancers are sequences that can be located far from the gene but boost transcription by interacting with transcription factors.

What is the difference between euchromatin and heterochromatin?

Euchromatin is loosely packed, relaxed DNA that is transcriptionally active, while heterochromatin is tightly packed, condensed DNA that is transcriptionally inactive.

How does histone acetylation affect gene expression?

Histone acetylation relaxes chromatin structure, making DNA more accessible for transcription, thereby activating gene expression. In contrast, deacetylation leads to gene repression.

What is the significance of the TATA box in gene transcription?

The TATA box is a promoter sequence that helps initiate transcription by binding transcription factors, which in turn recruit RNA polymerase to the gene.

How do hormones like cortisol affect gene expression?

Cortisol can regulate gene expression by binding to hormone response elements in DNA. It stimulates the transcription of catabolic enzymes, promoting processes like proteolysis and gluconeogenesis.

Outlines

00:00

🔬 Introduction to Gene Expression and Biochemistry Topics

This paragraph introduces the channel 'Medicos Perfect Net' and provides an overview of the biochemistry topics covered in previous videos. The focus is on DNA, RNA, and the processes of replication, transcription, and translation. It also teases the current topic of gene expression in eukaryotes, covering enhancers, promoters, transcription factors, and histone acetylation vs DNA methylation. The central dogma of molecular biology (DNA replication, transcription to RNA, and translation to protein) is briefly reviewed.

05:00

🧬 Differences Between Euchromatin and Heterochromatin

This section discusses euchromatin and heterochromatin, the two types of chromatin that impact gene transcription. Euchromatin is described as loose, relaxed, and open, making it accessible for transcription, while heterochromatin is condensed, closed, and inaccessible for transcription. The concept of nucleosomes is introduced, explaining how DNA wraps around histone proteins to form nucleosomes, which have a significant role in chromatin structure and gene accessibility.

10:01

🧪 Enhancers, Promoters, and Transcription Factors

The paragraph covers how transcription is initiated and regulated in cells. It discusses transcription factors, which bind to promoters (like the TATA box) on DNA to stimulate RNA production. Enhancers, which are regulatory elements located farther away from the gene, also help boost transcription. The difference between cis-regulators (promoters and enhancers close to the gene) and trans-regulators (transcription factors that can act from a distance) is clarified.

15:04

🔄 Hormone and Growth Factor Influence on Gene Expression

This section explores how hormones and growth factors, such as cortisol, can amplify gene expression. The two mechanisms highlighted are the use of enhancers and gene duplication. The paragraph explains how cortisol, a catabolic hormone, regulates gene expression by binding to hormone response elements on DNA and either stimulating or inhibiting the production of enzymes, depending on its goals (e.g., breaking down proteins, glycogen, or fats).

💊 Antibiotics and Bacterial Inhibition

The final paragraph briefly touches on the topic of antibiotics, which can inhibit bacteria by targeting their cell walls, membranes, protein synthesis machinery, or DNA. It promotes the speaker's antibiotics course available on their website and concludes with a call to action for viewers to subscribe and support the channel.

Keywords

💡Replication

Replication is the process of copying DNA to produce an identical DNA strand. It occurs during the S phase of the cell cycle. The video emphasizes that replication is a crucial step in maintaining genetic integrity across cell generations, where the enzyme DNA polymerase plays a key role.

💡Transcription

Transcription refers to the process of converting DNA into RNA. The video highlights RNA polymerase as the enzyme responsible for synthesizing different types of RNA (such as mRNA, tRNA, and rRNA) from a DNA template. Transcription is a major part of the central dogma of molecular biology.

💡Translation

Translation is the process by which mRNA is decoded by ribosomes in the cytoplasm to produce proteins. In the video, translation involves the ribosome using codons from mRNA and matching them with anticodons on tRNA to assemble a chain of amino acids, which form proteins. This is a critical step for protein synthesis in cells.

💡Enhancers

Enhancers are sequences of DNA that can boost the transcription of genes even though they may be located far from the gene they regulate. The video explains how enhancers act as 'recruiters' of transcription machinery, significantly increasing gene expression by interacting with transcription factors.

💡Promoters

Promoters are DNA sequences located near the start of a gene and play a key role in initiating transcription. The video mentions the TATA box, a common promoter sequence that helps position RNA polymerase to begin transcription. Promoters are crucial in regulating gene expression.

💡Histone Acetylation

Histone acetylation is a modification process where acetyl groups are added to histones, leading to a more relaxed chromatin structure (euchromatin). This allows DNA to be more accessible for transcription. The video emphasizes that acetylation makes DNA 'active,' facilitating gene expression.

💡DNA Methylation

DNA methylation is the addition of methyl groups to DNA, typically leading to gene silencing by making the chromatin structure more condensed (heterochromatin). The video uses the mnemonic 'methylation mutes DNA' to explain how methylation reduces gene accessibility and suppresses transcription.

💡mRNA

Messenger RNA (mRNA) is the RNA form that carries genetic information from DNA to the ribosomes, where it is translated into proteins. The video explains that mRNA starts as heterogeneous nuclear RNA (hnRNA) and undergoes post-transcriptional modifications (such as splicing, capping, and tailing) to become mature mRNA.

💡Post-transcriptional Modification

Post-transcriptional modification refers to the process that newly synthesized hnRNA undergoes to become mature mRNA. This includes the removal of introns (splicing), adding a 5' cap, and a 3' poly-A tail. These steps ensure that mRNA is stable and functional for protein synthesis, as mentioned in the video.

💡Transcription Factors

Transcription factors are proteins that bind to specific DNA sequences to regulate transcription. They have a DNA-binding domain and an activation domain. The video explains that transcription factors can either enhance or inhibit gene transcription by assembling the transcription machinery at the promoter.

Highlights

Introduction to control of gene expression in eukaryotes, including enhancers, promoters, transcription factors, and modifications such as histone acetylation and DNA methylation.

Explanation of the central dogma of molecular biology: DNA replication, transcription to RNA, and translation to proteins.

Difference between exons (expressed regions) and introns (non-coding regions), emphasizing the importance of splicing introns out during RNA processing.

Post-transcriptional modifications of RNA: adding a cap to the 5' end, a poly-A tail to the 3' end, and splicing out introns to create mature mRNA.

Post-translational modifications of proteins: addition of phosphate groups, carboxyl groups, oligosaccharides, hydroxyl groups, and lipids to form fully functional proteins.

Detailed description of chromatin structure: euchromatin is open and accessible for transcription, while heterochromatin is closed and dense, making it transcriptionally inactive.

DNA is wrapped around histone proteins, forming nucleosomes, which regulate the accessibility of DNA for transcription.

The process of transcription involves RNA polymerase, which transcribes DNA into RNA. Promoters, such as the TATA box, initiate transcription.

Role of transcription factors: proteins that bind to DNA at promoters and response elements to regulate the transcription of genes.

Difference between enhancers and transcription factors: enhancers are CIS-regulatory elements, while transcription factors are trans-regulatory elements.

Hormones and growth factors, such as cortisol, can amplify gene expression through enhancers and gene duplication.

Distinction between acetylation and methylation: acetylation activates DNA for transcription (euchromatin), while methylation silences DNA (heterochromatin).

Example of cortisol acting on hormone response elements to promote catabolic activities such as proteolysis, glycogenolysis, and lipolysis by stimulating transcription of related genes.

Quiz question on histone deacetylase: De-acetylation of histones leads to transcriptional inactivity by converting euchromatin into heterochromatin.

Conclusion encouraging viewers to continue studying the topic and offering downloadable antibiotic courses from the creator's website.

Transcripts

hey guys it's medicos is perfect net is

where medicine makes perfect sense let's

continue our biochemistry playlist in

previous videos we talked about DNA

versus RNA nucleosides versus

nucleotides purines versus pyrimidines

heterochromatin versus euchromatin we

talked about replication transcription

and translation the last video was the

control of gene expression in the

prokaryotes like the story of the Lac

operon but today it's the control of

gene expression in eukaryotes talk about

enhancers promoters transcription

factors acetylation of histones versus

methylation of DNA let's get started oh

by the way do not forget that the exons

are expressed but the intrones

intervenes that's why we splice them out

and we throw them in the trash please

watch the videos in this playlist in

order the central dogma what a dogma of

molecular biology when you copy the DNA

it's called replication it happens in

the S phase of the cell cycle when you

convert DNA into RNA it's called

transcription we can convert the DNA

into rrna which is the most abundant or

mRNA but before that it has to become H

and RNA or you can convert your DNA into

TRNA what's the name of the enzyme that

copies the DNA it's called DNA

polymerase what's the name of the enzyme

that converts DNA into RNA RNA

polymerase RNA polymerase 1 will give us

rrna RNA polymerase 2 will give us mRNA

RNA polymerase 3 will give us TRNA back

to mRNA story in the beginning It Was

Naive heterogeneous nuclear RNA young

and unwise but after

post-transcriptional modification it

will mature and grow up and will be able

to Bear the pain pain and suffering of

Life on its own it's not dependent on

the nucleus anymore it can leave mommy's

home to go to the outside Wilderness

outside the nucleus and into the

cytoplasm it will find the ribosomes on

the rough endoplasmic reticulum and the

ribosome will help us translate this

mRNA into proteins from meaningless

codons into meaningful amino acids what

are the steps of post-transcription

modification you supplies the bad guys

out kick the intro into the trash and

then add a cap at the five Prime end add

a tail at the three prime end how about

post-translational modifications of

proteins well you might need to add

phosphate groups carboxyl groups you

might need to add oligosaccharides

hydroxyl groups or lipid then my protein

will acquire its primary structure

secondary structure tertiary structure

and quaternary structure now we have a

functional protein ready to perform from

cellular functions because the cell is

the building unit of your body it's the

central dogma of Life bioology here's

the whole story baby here is my DNA the

original coding strand also known as

sense and then after replication you

copy it into another DNA called template

strand since it pairs with the original

we call this anti-sense and the original

one is called sense and then what take

this DNA template and make it into RNA

thank you RNA polymerase in the

beginning we have h n RNA and then after

post-transcriptional modification it

becomes mRNA mRNA has the lovely codons

like this they will be recognized by the

anticodons on the TRNA and the first

codon is Aug which codes for the amino

acid methion and then you keep putting

amino acids amino acids amino acids you

link them together via peptide bonds

thank you peptidil transferase enzyme

and your peptide chain will keep getting

longer and longer and longer here's an

amino acid two together dipeptide three

together tripeptide oligopeptide

polypeptide protein Etc until you hit a

wall this top codon could be you a a u g

a or UAG you are gone you go away you

are away and then my peptide chain will

terminate and will leave the chat I mean

the ribosome where do you think DNA

replication happens in the nucleus how

about transcription in the nucleus today

we're talking about factors that can

affect transcription in the nucleus how

many types of chromatin do we have well

when my DNA is loose and relaxed and

wide open like this we call it

euchromatin but when my DNA is wrapped

gazillion times on itself it becomes

dense head

heterochromatin eochromatin is relaxed

and open heterochromatin is condensed

and closed here chromatin is accessible

I can work with this I can transcribe

this but the heterochromatin it's not

going to happen it's inaccessible

because your chromatin is relaxed and

open it appears lighter under the

microscope versus heterochromatin which

is condensed that's why it appears

darker and thicker and what's the name

of the protein around which I wrapped my

DNA it's called the histo it's not just

one protein there are many proteins and

we talked about them before DNA plus

histone equals nucleosome which has a

Soma a body made of histones to A to B 3

and 4 and it has what around it nucleic

acid that's why it's called nucleosome

DNA is your nucleic acid it is

negatively charged it is a double helix

usually right-handed it has polarity

it's anti-parallel five Prime three

Prime versus three prime five Prime

phosphate is always at the five Prime

phosphate is a great source of energy

that's why we always go from five Prime

to three prime because I need my

phosphate DNA replication adds

nucleotides from five Prime to three

prime transcription same story five to

three translation also five to three

beautiful this is the story of DNA

transcription what is transcription

transcriptionists take the DNA template

and make it into RNA who's the hero RNA

polymerase or if you want to be

sophisticated DNA dependent RNA

polymerase I'm adding Polymers of RNA

and I read the message that was on the

DNA okay near the beginning of the

template strand what do we have the

promoter the Tata box thiamine adenine

thiamine adenine and just like Tata the

Tycoon from India promotes all kinds of

business activities the Tata box on your

DNA promotes all kinds of transcription

which means the making of RNA

transcription factors what are they they

are proteins what do they do well they

stimulate transcription they assemble

the transcription Machinery they help

you make RNA from DNA where can I find

them at the promoter Oh you mean the

Tata box on the DNA exactly these

transcription factors have two parts a

DNA binding domain and activation domain

the DNA binding domain guess what it's

gonna bind DNA exactly at the promoter

or the response elements as for the

activation domain it's a domain that

activates and stimulates The Binding of

more transcription factors and more

regulatory proteins to the DNA so that

you can boost transcription if you want

that or inhibit transcription if you

want that regulation baby but how many

courses what are these response elements

well the response elements are elements

that help you trigger a response no duh

such as the enhancers unlike

transcription factors enhancers are

outside the promoter not at the promoter

mnemonic time enhancers are eccentric to

the promoter away from the promoter and

still they are proteins because the

active thing in your cell or in your

body is mostly a protein all your

receptors are proteins all your channels

are proteins all your pumps are proteins

all your carriers are proteins the vast

majority of your enzymes are proteins

etc etc etc in fact the more active the

cell the greater the protein percentage

in the cell and in the cell membrane so

it's not shocking that the enhanced are

proteins and it's not shocking that the

transcription factors are proteins

enhancers are response elements what do

you mean by response element a sequence

of your DNA that binds only to specific

transcription factors they are

recruiters they recruit the Machinery of

transcription which will boost your

transcription I.E making RNA using a DNA

template there is a difference between

enhancers and transcription factors

enhancers are CIS Regulators but

transcription factors are trans

Regulators what do you mean by that CIS

means the same they are in the same

vicinity as the J and they control close

by however trans Regulators are far away

farther away from the gnd control and

that's why trans Regulators have to

travel all the way until they reach the

gene that they want to control I.E the

site of action but CIS Regulators are at

the same vicinity and they include

promoters I know that enhancers I've

heard of that and response elements what

do they do they regulate the sequence of

bases on your DNA which is the essence

of transcription next did you know that

many hormones and many growth factors

can amplify gene expression how do they

do it two main mechanisms number one

using enhancers number two Gene

duplication you can duplicate genes in

series or in parallel in series means

it's happening on the same chromosome

and I keep adding more genes and many

copies hundreds of copies in a row on

the same chromosome or I can do it in

parallel to do it in parallel I gotta

separate the strands via helicase and I

will get as many copies as I want

parallel to the chromosome that I acted

upon another distinction is enhancers

versus promoters promoters must be very

close to the start of the gene remember

my Tata box it was very close if you

remember the location it was negative 25

because it was to the left I.E Upstream

from the first Gene that will become the

first nucleotide 25 is closed so we're

still close but enhancers could be a

little further let's say up to 1000

bases from the start of the Gene and

that's a big difference so promoter is

right there enhancer a little further

transcription factors way far away from

the dream another distinction

acetylation of histones versus

methylation of DNA mnemonic time

acetylation will make your DNA active

but methylation will make it mute what

do you mean by active DNA I mean

neochromatin open relaxed and accessible

and transcribable and what do you mean

by mute DNA I mean hetero chromatin

closed condensed inaccessible if the

enhancer response elements thing is not

making sense to you consider this

remember in my Endocrinology playlist as

well as in my biology playlist I've told

you that insulin is one land any other

hormone is the opposite of insulin and

by other hormones I mean glucagon

cortisol epinephrine and thyroxine let's

take cortisol for example what does

Cortisol want it's a catabolic hormone

it wants to break down stuff break down

proteins into amino acids break down

glycogen into glucose break down the

baked fats into small fats from the big

to the small that's catabolism so here

is the lovely cortisol wants to perform

its catabolic function how does it do it

well here score is all in the

bloodstream cortisol will reach the cell

since cortisol is a fat hormone lipid

hormone it is lipid soluble and your

cell membrane is lip paid by layer lipid

will be able to diffuse through lipid no

problem whatsoever it will find its

nucleus in the cytoplasm amazing and

then after cortisol binds the nucleus

they will go together into the nucleus

acting upon what hormone responds

elements elements that trigger response

I.E a sequence of my DNA that binds

specific transcription factors remember

the story of the zinc finger which will

help us do what transcription baby

modulate gene expression regulation by

regulation do you mean stimulation or

inhibition it depends cortisol will

stimulate every enzyme that is catabolic

because cortisol is acting in his own

self-interest so all the enzymes that

promote proteolysis will be stimulated

all the enzymes that promote

glycogenolysis will be stimulated all

the enzymes that promote gluconeogen

Genesis will be stimulated and all the

enzymes in lipolysis will be stimulated

but all of the other enzymes that were

anabolic will be inhibited that is the

essence of regulation of your

transcription what a beautiful story

quiz time which of the following is true

about the effect of histone D acetylase

is it A B C or D please pause the video

and take about 10 seconds to think about

it and then I'll tell you the answer now

please pause are you ready let's go

which of the following is true about

histone the acetylase let's break that

down d means what removal of it means no

acetylation and you know that

acetylation makes the DNA active so

de-acetylation means inactive what do

you mean by inactive I mean

heterochromatin condensed closed and

inaccessible making D the correct answer

d as in doofus there are many ways to

get rid of bacteria antibiotics are one

of them some of them affect the

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bacterial cell membrane others affect

the protein making Machinery protein

synthesis Inhibitors and others directly

inhibit the DNA of the bacteria you can

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miraclesperfectsnetis.com no

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perfect sense