Beta Globin Gene Cluster
- 1. In The Name of God Subject : Beta Globin gene cluster Alireza Kazemi
- 2. Hemoglobin Heme = Protoporphirin + 𝑭𝒆 𝟐+ Hemoglobin Alpha Globin Beta
- 3. Globins 16p13.3 Alpha Cluster Telomeric end 30 kb Globins 11p15.5 Beta Cluster near the Telomeric end 70kb
- 4. Human Globin Genes 3 Exons (coding) IVS-1 Short (120-130bp) 2 Introns (Non-coding) IVS-2 Long (850-900bp) Promoter 𝟑′ and 𝟓′ UTR Enhancer Silencer
- 5. Exon Function Exon1 Removing Globin mRNA from cell nuclear Exon2 Junction to Heme Exon3 Junction to other globins
- 10. Transcription Factors for Globin synthesis AP-1,SP-1 General YY-1,USF SCL,TAL-1 TFs LCR-F1 , EKLF , ATXR Specific GATA-1 , FOG NFE 2 , Nrf 1 , Nrf 2
- 11. Regulatory regions in globin genes 1) Basal Promoter +32 to -37 2) Upstream Regulators (UR) -40 to -250 3) Proximal Enhancers in 3’ end of β and γ globin genes 4) Master Regulators Alpha cluster HS (MCS-R) Beta cluster β-LCRs
- 12. Basal Promoter in Beta Globin Gene TFIIB Beta-DRF TBP TFIID (TAF) RNA Polymerase II Mutation in Promoter Stop Expression β -Thalassemia -31 +1 +27 +32 BRE TATA Inr MTE DPE -37 Sequence :
- 13. Upstream Regulators (UR) in Beta Globin genes -250 -40 GATA-1 EKLF NF-Y CP-1 β -DRF TFIIB BP2bs NF1bs GATA BB1bs CACC CACC CCAAT β -DRE β -DRE
- 14. Enhancers Proximal = 3’ end enhancers in β and γ globin genes Enhancers Distal = Master regulators : LCR and HS
- 15. Proximal Enhancers at 3’ end of Beta and Gama globin Genes HBB : HBG1: Mutation in Enhancers β -ThalassemiaDown expression γPE
- 16. LCR Locus control regions (LCR) are operationally defined by their ability to enhance the expression of linked genes to physiological levels in a tissue-specific and copy number-dependent manner at ectopic chromatin sites .
- 17. β-LCRs β-LCRs containing five areas that are sensitive to DNAse1 erythroid SpecificDnase1Hypersensitive Site (eDHS) HS-1 HS-2 eDHS HS-3 HS-4 HS-5
- 18. β-LCRs HS-2 The most important area in increasing the globin chain synthesis HS-3 The most important area in remodelling and opening chromatin structure
- 20. LCR Motifs Each of the LCRs have a different number of these sequences : GATA GATA-1 CACC SP-1 and EKLF LCR Motifs MARE E-BOX SCL(TAL-1) YY1bs SP1bs
- 21. MARE Sequence Sequence : TGAGTCA Has an inhibitory and silencing roles in beta globin transcription Junction to basic leucine zipper factors AP-1 (bZIP) NF-E2 Bach-1 Nrf-1/LCRF1
- 22. MARE Sequence Function In Lower Heme levels In Higher Heme levels Bach1 + Small maf NF-E2/Nrf2 + Small maf (P45) (P18) Junction to Enhancers Junction to MARE sequence Globin expression Inhibition of Globin synthesis Hemoglobin
- 24. HRI kinase
- 25. GATA-1 Functions : Regulation of globin synthesis Regulation of Heme synthesis Regulation of other erythroid transcription factors Regulation of hematopoiesis ( MKs , Eo , … )
- 26. Regulation of globin synthesis By GATA-1 Junction to 5’ end Silencer in ε genes Down expression of ε gene Hb Gower Junction to γ Glycine Silencer Down expression of γ gene (HbF ) Intraction with other TFs (e.g. GATA-2 , FOG , EKLF , P300/CEP and PU-1)
- 27. GATA-1 Connect to multiple sequences of the promoter and Enhancer in beta globin gene cluster Loop Formation increase β-Globin gene expression
- 28. GATA-1
- 29. GATA-1 GATA-1 P300/CEP GATA-1 acetylation Histone acetylation Increase access to Beta globin gene
- 30. EKLF Erythroid Krueppel-Like Factor Functions 1. Chromatin remodeling 2. Modulation of the gamma to beta globin switch 3. Transcriptional activation 1. EKLF Three Forms 2. Fetal form (FKLF) 3. Basic form(BKLF)
- 31. EKLF • Globin expression In Adult(α & β) EKLF In Embryo & Fetal FKLF BKLF • EKLF BKLF • EKLF Mutation BKLF & Globin EKLF Over expression Thrombocytopenia Early switch γ to β
- 32. NF-E2 • Consists of two components : 1. P45 Nrf 1,2,3 Bach 1,2 2. P18 Small maf (maf-k) • Functions Globin synthesis Heme synthesis ferrochelatase PBG Deaminase
- 33. P45 Functions Junction to CEP/P300 , Ubiquitin ligase , TAFII-130 Open chromatin structure of target genes Increase access to TFs (e.g. GATA-1, EKLF, SCL) Globin expression Inhibition of Methyltransferase MLL2 (myeloid/lymphoid or mixed-lineage leukemia protein 2 )
- 35. Switching to HbA • In ε & γ genes UR : 2 Motifs Enhancer SSE(Stage Selector Element) Silencer DR-1 DR-1 DRED
- 36. Switching to HbA • In β-Globin regulatory elements : 11 GATA motifs GATA The sharp increase β-Globin gene expression 4 CACC-box EKLF
- 37. Drug effects • γ - Aminobutyric acid(GABA) Butyrate Phenylbutyrate HDAC & P300 inhibition Valproic acid Histone Acetylation HbF