Chromatin modulation and role in gene regulation

DNA Packaging

1. Chromatin Modulation and its Role in Gene R egulation

2. Presented By: MUHAMMAD Zain Ahsan Amber Ayyaz Talha Mazhar Hamza Khan

3. Contents: Introduction DNA to Chromosome Chromatin structure Types of chromatin Functions of chromatin Chromatin re-modeling Chromatin re- modeling methods Chromatin role in gene regulatio n Importance of gene regulation

4. I ntroduction The DNA in eukaryotic cells is extensively folded and packed into the protein-DNA complex called chromatin . Histones proteins are an important part of this complex. DNA protein complex is called nucleosome. Walther Fleming discovered chromatin in 1878 while study cell division. He stained the cells of salamander with alanine dye. He observed that some portion of genetic material absorbed dye more than other parts. He named it chromatin ( Chroma is Greek word mean color)

5. Walther Fleming stained chromatin

6. DNA to Chromosome

7. Chromatin structure in cell cycle

8. Types of chromatin Two types of chromatin In 1928 Emil hitez used term euchromatin and heterochromatin Euchromatin It is a loosely packed form of chromatin and rich in gene concentration. It is comprises the most active portion of genome It is truly transcribing portion of DNA. This portion is called “ string on the beads” This structure appears mostly in interphase or growth phase of the cell cycle.

9. H eterochromatin It is tightly packed form of the chromatin. This region of chromosome is more condensed and stained deeply with different dyes. Two basic types 1. Facultative Heterochromatin It comprises most of the silenced genes 2. Constitutive Heterochromatin It makes the structural and functional forms of chromosome like Centromere Telomere Bothe are involved in gene expression. Both are transcriptionally inactive.

10. Role of chromatin DNA packaging into more compact form Reinforce the DNA macromolecules to allow mitosis Prevent DNA from damaging Regulation of gene expression Regulation of DNA replication

11. Chromatin re modeling What is meant by Re-Modeling ? Why we need it ? Why chromatin compaction occur ? why gene containing portion of DNA wrapped on Histones? What are histones ? Two types 1.Core histones proteins 2.Linker histone proteins Dimerization Homodimer Heterodimer

12. Chromatin Re- Modeling Methods Direct nucleosome mobilization method It is a ATP dependent method SWI/SNF complex is involved SNF specific for sucrose fermenting gene This complex require some transcriptional factors for activity. SWI/SNF can modulate chromatin by 3 mechanisms It recognize the acetylated histone protein Nucleosome disruption Nucleosome sliding Nucleosome transfer

13. Nucleosome disruption Inactive ground state ATP Derepressed state More accessible Closed

14. Three possible activities of Swi/Snf Nucleosome remodeling Nucleosome sliding Octamer transfer TF TF TF TF TF TF

15. Histone modifications Histone can be modified by Methylation Acetylation Phosphorylation Ubiquitnation De methylation

16. Chromatin role in gene regulation Positive control Transcription on Activation occurs due to Readers Writers Negative control Transcription off Repression occurs due to erasers

17. Importance of gene regulation Control the amount of gene product Allow cells to adjust with changing conditions Expression of gene at proper time. Prevent the wastage of cell energy.