Slide 1

Genetics and Evolution: Molecular Basis of Inheritance

• Topic: Role of Sigma factor in transcription
• Importance of understanding transcription process
• Introduction to Sigma factor
• Function of Sigma factor in RNA synthesis
• Significance of Sigma factor in regulating gene expression

Slide 2

Transcription: Introduction

• Definition of transcription
• Importance of transcription in gene expression
• Comparison between transcription and DNA replication
• Key players in the transcription process: RNA polymerase and Sigma factor
• Types of RNA molecules synthesized during transcription

Slide 3

RNA Polymerase: The Transcription Enzyme

• Definition of RNA polymerase
• Structure and subunits of RNA polymerase
• Role of RNA polymerase in producing RNA from DNA template strand
• Process of RNA synthesis by RNA polymerase (initiation, elongation, termination)
• Importance of RNA polymerase in gene expression

Slide 4

Sigma Factor: Overview

• Definition of Sigma factor
• Subunit composition of bacterial RNA polymerase holoenzyme
• Role of Sigma factor in determining promoter specificity
• Classification of Sigma factors in bacteria
• Sigma factor function in gamma proteobacteria

Slide 5

Sigma Factor in Transcription Initiation

• Importance of specificity in transcription initiation
• Role of Sigma factor in recognizing and binding to promoters
• Different Sigma factors and their affinity to specific promoters
• Role of Sigma 70 factor in E. coli transcription initiation
• Detailed mechanism of Sigma factor-mediated transcription initiation

Slide 6

Sigma Factor in Transcription Elongation

• Overview of transcription elongation process
• Role of Sigma factor during transcription elongation
• Sigma factor dissociation from RNA polymerase during elongation
• Impact of Sigma factor release on RNA synthesis
• Regulation of transcription elongation by Sigma factor

Slide 7

Sigma Factor in Transcription Termination

• Importance of termination in transcription process
• Role of intrinsic and factor-dependent termination mechanisms
• Role of Sigma factor in termination processes
• Detailed mechanism of Sigma factor-mediated termination
• Impact of Sigma factor on gene expression through termination

Slide 8

Sigma Factor vs. Transcription Factors

• Definition and role of transcription factors
• Comparison between Sigma factor and transcription factors
• Function of Sigma factor in prokaryotic transcription
• Activities and regulation of transcription factors in eukaryotes
• Interplay between Sigma factor and transcription factors in gene regulation

Slide 9

Role of Sigma Factor in Gene Expression

• Overview of gene expression regulation
• Influence of Sigma factor on gene expression
• Regulation of Sigma factor activity and abundance
• Impact of Sigma factor mutations on gene expression
• Significance of studying Sigma factor in understanding genetics and evolution

Slide 10

Summary

• Recap of the key points discussed about Sigma factor
• Importance of Sigma factor in transcription
• Role of Sigma factor in initiation, elongation, and termination
• Comparison between Sigma factor and transcription factors
• Significance of understanding Sigma factor in gene expression regulation

Regulation of Sigma Factor Expression

• Levels of Sigma factor expression are controlled by transcriptional regulation
• Environmental signals and cellular cues influence Sigma factor gene expression
• Regulatory proteins and transcription factors modulate Sigma factor promoter activity
• Positive and negative feedback loops regulate Sigma factor expression
• Changes in Sigma factor expression levels affect gene expression dynamics

Slide 22

Post-Translational Modifications of Sigma Factor

• Sigma factors can undergo post-translational modifications
• Phosphorylation of Sigma factors regulates their activity
• Phosphorylation is catalyzed by protein kinases
• Phosphorylated Sigma factors can exhibit altered affinity for promoters
• Post-translational modifications provide additional layers of Sigma factor regulation

Slide 23

Sigma Factor Competition and Promoter Usage

• Multiple Sigma factors can compete for binding to RNA polymerase
• Relative affinity of different Sigma factors dictates promoter usage
• Promoters with different Sigma factor binding sites result in distinct gene expression patterns
• Sigma factor competition is influenced by environmental conditions and cellular factors
• Competing Sigma factors determine the activation or repression of specific gene programs

Slide 24

Sigma Factor and Bacterial Adaptation

• Sigma factors play a crucial role in bacterial adaptation
• Different Sigma factors respond to specific environmental cues
• Changes in Sigma factor expression enable bacteria to survive and thrive in different conditions
• Examples of Sigma factor involvement in stress response and nutrient utilization
• Understanding Sigma factor regulation aids in developing strategies to combat bacterial infections

Slide 25

Sigma Factor Evolution and Genetic Variation

• Sigma factors exhibit significant sequence and functional diversity among bacteria
• Gene duplication events and horizontal gene transfer contribute to Sigma factor evolution
• Natural selection acts on Sigma factors to optimize gene expression and adaptability
• Genetic variation in Sigma factors leads to phenotypic diversity and evolutionary success
• Comparative genomics help in studying the evolution of Sigma factors across species

Slide 26

Example: Sigma 32 Factor and Heat Shock Response

• Sigma 32 factor is involved in regulating heat shock response in bacteria
• Heat shock induces the synthesis of Sigma 32 factor
• Sigma 32 factor directs RNA polymerase to transcribe genes involved in heat shock response
• Heat shock proteins are produced, aiding in protein folding and stress adaptation
• Understanding Sigma 32 factor function provides insights into cellular response to heat stress

Slide 27

Example: Sigma 54 Factor and Nitrogen Metabolism

• Sigma 54 factor is involved in nitrogen metabolism regulation
• Sigma 54 recognizes specific promoters involved in nitrogen assimilation
• Gene expression program controlled by Sigma 54 factor enables efficient nitrogen usage
• Mutations in Sigma 54 factor or its regulatory proteins can disrupt nitrogen metabolism
• Studying Sigma 54 factor helps in improving nitrogen utilization in agriculture

Slide 28

Equation: Transcription Initiation

Promoter DNA + RNA polymerase-holoenzyme + NTPs → Open complex + Initiation of RNA synthesis

• Promoter DNA contains -35 and -10 regions recognized by the Sigma factor
• RNA polymerase-holoenzyme consists of RNA polymerase and associated Sigma factor
• NTPs (ribonucleotide triphosphates) serve as substrates for RNA synthesis
• Open complex formation involves the separation of DNA strands at the transcription start site
• Initiation of RNA synthesis occurs with the addition of the first nucleotide to the growing RNA molecule

Slide 29

Equation: Transcription Elongation

RNA polymerase complex + Elongation NTPs → RNA synthesis + Template DNA strand movement

• RNA polymerase complex includes the elongating RNA polymerase without the Sigma factor
• Elongation NTPs (ribonucleotide triphosphates) provide the building blocks for RNA synthesis
• RNA synthesis involves the addition of complementary nucleotides to the growing RNA molecule
• Template DNA strand movement occurs as RNA polymerase advances along the DNA template
• Template DNA strand rewinds after the passage of RNA polymerase

Slide 30

Equation: Transcription Termination

Transcripts + Termination signal → RNA polymerase release + Termination of RNA synthesis

• Transcripts refer to the completed RNA molecules synthesized during elongation
• Termination signal can be intrinsic or factor-dependent
• Intrinsic termination involves the formation of an RNA hairpin structure and a termination sequence
• Factor-dependent termination requires additional factors, such as rho factor
• RNA polymerase release occurs upon termination, leading to the termination of RNA synthesis