Control of Gene Expression in Eukaryotes

This set of flashcards covers critical concepts in the control of gene expression in eukaryotes, examining mechanisms from transcription initiation to post-transcriptional regulation and implications in disease.

What is the role of the mammalian pre-initiation complex in gene transcription?

It must be assembled every time a gene is transcribed and contains RNA polymerase along with more than a dozen subunits and over 100 polypeptides.

What is differential gene expression?

The process responsible for forming specialized cell types, arranging them into tissues, and coordinating their activity in multicellular organisms.

How do eukaryotes regulate gene expression?

At the levels of transcription, translation, and post-translation, with additional control through chromatin remodeling and RNA processing.

What is chromatin remodeling?

The process of decondensing chromatin to expose DNA for transcription.

What is the TATA box?

A key core promoter sequence in eukaryotes where RNA polymerase binds to initiate transcription.

What is the function of enhancers in gene regulation?

Enhancers are regulatory DNA sequences that facilitate transcription by binding transcriptional activators, even from large distances from the promoter.

What roles do histone acetyltransferases (HATs) and histone deacetylases (HDACs) play in gene regulation?

HATs promote decondensed chromatin associated with active transcription while HDACs promote condensed chromatin and inhibit transcription.

What is alternative splicing?

A post-transcriptional mechanism allowing a single gene to produce multiple mRNA variants by including or excluding certain exons.

How does RNA interference (RNAi) regulate gene expression?

By using small RNA molecules to bind to complementary mRNA sequences, leading to either destruction of the mRNA or inhibition of its translation.

What is the significance of tumor suppressor genes like p53?

They encode proteins that regulate the cell cycle and repair DNA damage; mutations in these genes can lead to cancer.

What is epigenetic inheritance?

The inheritance of gene expression patterns that are not due to changes in DNA sequence, often mediated by modifications to chromatin.

What is the relationship between gene regulation and cancer?

Many cancers are caused by mutations that lead to the loss of function of tumor suppressor genes or activation of oncogenes, resulting in uncontrolled cell growth.

Describe the role of transcription factors in eukaryotic gene expression.

Transcription factors bind to specific DNA sequences and are critical for regulating the transcription of genes.

What distinguishes eukaryotic from bacterial gene expression regarding operons?

Eukaryotes typically do not use operons; instead, they have separate regulatory elements for each gene.

What is one way post-translational control occurs?

By adding chemical groups such as phosphates to proteins, thereby altering their activity.

How does chromatin structure influence gene expression?

Chromatin must be decondensed to allow access to DNA for transcription, and this structure is regulated by DNA and histone modifications.

What is the Mediator in transcription initiation?

A large protein complex that integrates signals from various transcription factors and facilitates the assembly of the pre-initiation complex.

Explain how the phosphorylation of proteins affects cellular function.

Phosphorylation can activate or deactivate proteins, influencing their roles in cellular pathways such as signaling and cell division.

What is the role of the mammalian pre-initiation complex in gene transcription?

It must be assembled every time a gene is transcribed and contains RNA polymerase along with more than a dozen subunits and over 100 polypeptides.

What is differential gene expression?

The process responsible for forming specialized cell types, arranging them into tissues, and coordinating their activity in multicellular organisms.

How do eukaryotes regulate gene expression?

At the levels of transcription, translation, and post-translation, with additional control through chromatin remodeling and RNA processing.

What is chromatin remodeling?

The process of decondensing chromatin to expose DNA for transcription.

What is the TATA box?

A key core promoter sequence in eukaryotes where RNA polymerase binds to initiate transcription.

What is the function of enhancers in gene regulation?

Enhancers are regulatory DNA sequences that facilitate transcription by binding transcriptional activators, even from large distances from the promoter.

What roles do histone acetyltransferases (HATs) and histone deacetylases (HDACs) play in gene regulation?

HATs promote decondensed chromatin associated with active transcription while HDACs promote condensed chromatin and inhibit transcription.

What is alternative splicing?

A post-transcriptional mechanism allowing a single gene to produce multiple mRNA variants by including or excluding certain exons.

How does RNA interference (RNAi) regulate gene expression?

By using small RNA molecules to bind to complementary mRNA sequences, leading to either destruction of the mRNA or inhibition of its translation.

What is the significance of tumor suppressor genes like p53?

They encode proteins that regulate the cell cycle and repair DNA damage; mutations in these genes can lead to cancer.

What is epigenetic inheritance?

The inheritance of gene expression patterns that are not due to changes in DNA sequence, often mediated by modifications to chromatin.

What is the relationship between gene regulation and cancer?

Many cancers are caused by mutations that lead to the loss of function of tumor suppressor genes or activation of oncogenes, resulting in uncontrolled cell growth.

Describe the role of transcription factors in eukaryotic gene expression.

Transcription factors bind to specific DNA sequences and are critical for regulating the transcription of genes.

What distinguishes eukaryotic from bacterial gene expression regarding operons?

Eukaryotes typically do not use operons; instead, they have separate regulatory elements for each gene.

What is one way post-translational control occurs?

By adding chemical groups such as phosphates to proteins, thereby altering their activity.

How does chromatin structure influence gene expression?

Chromatin must be decondensed to allow access to DNA for transcription, and this structure is regulated by DNA and histone modifications.

What is the Mediator in transcription initiation?

A large protein complex that integrates signals from various transcription factors and facilitates the assembly of the pre-initiation complex.

Explain how the phosphorylation of proteins affects cellular function?

Phosphorylation can activate or deactivate proteins, influencing their roles in cellular pathways such as signaling and cell division.

What are General Transcription Factors (GTFs)?

Proteins that bind to the core promoter near the transcription start site and are essential for the transcription of all protein-coding genes by RNA polymerase II.

What are specific transcription factors?

Regulatory proteins that bind to enhancers or silencers to control the transcription of particular genes, often in a tissue-specific or developmental-stage-specific manner.

What is a proximal promoter element?

A regulatory DNA sequence located just upstream of the core promoter, often serving as a binding site for specific transcription factors to modulate gene expression.

What are silencers in gene regulation?

Regulatory DNA sequences that, when bound by specific repressor proteins, inhibit gene transcription, often acting from a distance.

What are insulators in gene regulation?

DNA sequences that prevent inappropriate interactions between genes and their regulatory elements, ensuring that enhancers activate only their appropriate target genes.

What is a nucleosome?

The basic repeating unit of chromatin, consisting of about 146 base pairs of DNA wrapped around a core of eight histone proteins.

How does histone methylation affect gene expression?

Methylation of histones can either activate or repress gene transcription depending on which amino acids are methylated and the degree of methylation; it often leads to chromatin condensation and gene silencing.

What is DNA methylation?

The addition of a methyl group to cytosine bases in DNA, typically occurring in CpG islands, which usually leads to long-term gene silencing without changing the DNA sequence itself.

How are DNA methylation patterns inherited during cell division?

After DNA replication, maintenance methyltransferases recognize hemimethylated DNA (one strand methylated, one new unmethylated) and methylate the new strand, preserving the epigenetic mark.

What is the function of the 5' cap on eukaryotic mRNA?

The 5' cap (a modified guanine nucleotide) protects the mRNA from degradation, facilitates its export from the nucleus, and helps in the initiation of translation.

What is the function of the poly-A tail on eukaryotic mRNA?

The poly-A tail (a chain of adenine nucleotides at the 3' end) helps protect the mRNA from degradation, aids in nuclear export, and promotes translation initiation.

What is a spliceosome?

A large and complex molecular machine composed of small nuclear RNAs (snRNAs) and proteins that removes introns from pre-mRNA and splices exons together during RNA processing.

What are microRNAs (miRNAs)?

Small non-coding RNA molecules that regulate gene expression post-transcriptionally by binding to complementary sequences on target mRNAs, leading to their degradation or translational repression.

What is ubiquitination in the context of protein regulation?

The process of covalently attaching ubiquitin proteins to a target protein, often marking it for degradation by the proteasome or influencing its activity, localization, or interactions.

What is the proteasome?

A large protein complex responsible for degrading ubiquitinated proteins within the cell into smaller peptides, playing a crucial role in protein turnover and cellular regulation.

What is X-inactivation?

An epigenetic process in female mammals where one of the two X chromosomes is randomly inactivated in each somatic cell, leading to dosage compensation for X-linked genes.

What is genomic imprinting?

An epigenetic phenomenon where only the gene inherited from a specific parent (either mother or father) is expressed, while the other allele is silenced through mechanisms like DNA methylation.

What is an enhanceosome?

A complex of multiple transcriptional activators and co-activators that assemble on an enhancer sequence, synergistically increasing the rate of gene transcription.

What are pioneer transcription factors?

Transcription factors that have the ability to bind to their specific DNA recognition sites even within condensed chromatin, initiating chromatin remodeling and opening access for other regulatory proteins.

What is the role of nuclear pores in gene expression?

Nuclear pores are channels embedded in the nuclear envelope that regulate the transport of molecules, including mature mRNA, from the nucleus to the cytoplasm for translation.

What factors influence mRNA stability?

mRNA stability is influenced by the length of the poly-A tail, specific sequences in the 3' untranslated region (3' UTR), binding of RNA-binding proteins, and the presence of microRNAs.

How does gene expression regulate cell differentiation?

Differential gene expression, controlled by cascades of transcription factors and epigenetic modifications, directs cells to develop into specialized types by activating specific sets of genes critical for their unique functions and structures.