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Eukaryote Gene Regulation Kayla Latta (Complexity (Chromatin Structure…
Eukaryote Gene Regulation Kayla Latta
Complexity
Cell Differentiation
Development of Organism
Chromatin Structure
If binding proteins have ACCESS to DNA
Loosely coiled
Active areas
Balbiani Rings
Puffs
DNasel Hypersensitive Sites
Small region typically upstream from start of transcription
Binding sites for regulatory proteins
Missing Nucleosome
RNA Processing
Levels
2) Initiation of Transcription
Transcription Factors
Activators
Repressors
• Interact with other proteins
• Be modified (resulting in altered action)
• Be localized (different ones present in different places)
• Be degraded
Transcription Factor Binding Sites
Insulators
3) RNA Processing & Stability
RNA Splicing
Intron removal
RNA Degradation
RNA Interference
1) Changes in Chromatin
Modification of Histones
2 Domains of Structure
Globular - interacts with other histones and the DNA
Positively charged tail areas interact with phosphate groups on DNA
Modification: Methylation of tails of histones
Can either increase or decrease transcription depending on which amino acids are methylated
Modification: Acetylation of tails of histones
Weakens interaction
with DNA and may allow transcription factors to bind DNA
Histone Deacetylation (lys)
– Enzyme: Histone
Deactylases (HDAC)
– Tightens association
between histones and DNA
Histone Acetylation (lys)
– Enzyme: Histone Acetyl Transferase (HAT)
– Loosens DNA – histone association by neutralizing the positive charge on the histones
Chromatin Remodeling
1) Repositioning the nucleosomes along the DNA so that DNA can change from being part of the nucleosome to part of the area between nucleosomes.
.
2) Conformational changes in the DNA or nucleosomes to allow the DNA bound to the nucleosome to be more exposed and more able to bind transcriptional activators.
DNA Methylation
.
Histone Methylation can activate or repress expression of a gene (usually repress)
DNA methylation by DNA methyl transferences tends to cause genes to be turned off (silencing)
– 5’-CG-3’ is the recognition sequence called CpG
• 5’-GC-3’ not recognized.
– 5mC ,common at CpG islands near the start of transcription
– Heavily methylated causes silencing
– Methylated CpG sequences “attracts” deacetylases further
repressing transcription since deacetylases remove acetyl
groups from histone tails
5’ – MC G – 3’
3’ – G MC – 5’
4) Protein Modification
