HIF-1 Gene is transcribed in the nucleus with the help of specific protein .HIF-1 protein with DNA binding activity. Functional HIF transcription factors comprise 2 different subunits, that is, alpha (α) and beta (β). The α subunit, of which there are 3 forms ( HIF-1α, HIF-2α and HIF-3α) out of which HIF-1α and HIF-2α are main, HIF-1α is oxygen sensitive, HIF-1α is expressed in almost all cell types, and transcriptionally upregulates a large number of genes, including those encoding Vascular endothelial growth factor (VEGF), Glucose transporters, Glycolytic pathway enzymes , Insulin-like growth factor-2, Endothelin-1, transferrin,  HIF-2  is the primary regulator of EPO production and also plays an important role in enterocyte iron uptake. HIF-β is continuously transcribed and its mRNA and protein are maintained at constant levels irrespective of oxygen levels, the availability of HIF-α is highly dependent on cellular oxygen levels. Thus, the activity of the HIF transcription factor heterodimer is relatively low under normal tissue oxygen conditions called normaxia however, as cellular oxygen levels decrease called hypoxia, HIF-α concentration increases, making HIF progressively more functionally active.

1. By: Amit
Roll no. 33
How cell sense and adapt to oxygen availability

2. ABOUT
 Peter J. Ratcliffe
He work on regulation of EPO in kidney in oxford university
in 1989.
 William G. Kaelin
Worked on VHL tumor, he hypothesized that their may be a
connection between VHL tumor and deficiency of the body
to detect oxygen in 1993
 Gregg L. Semenza
In 1992 GL. Semenza and wang identified the gene that
expressed HIF-1 alpha protein.

3. EPO (ERYTHROPOIETIN)
 Erythropoietin, also known as haematopoietin or
haemopoietin,
 It is a glycoprotein secreted by the kidney in
response to cellular hypoxia.
 it stimulates red blood cell production in the bone
marrow.
 Low levels of EPO are constantly secreted
sufficient to compensate for normal red blood cell
turnover.
 It used in case of anemia.
It also used by some sportsman as a performance
enhancer drug. (dopping)

4. *It also used by some sportsman as a performance enhancer drug. (dopping)

5. GENERAL PATHWAY

6. INTRODUCTION OF HIF-1
HIF-1 Hypoxia Inducible Factor – 1
HIF-1 Gene is transcribed in the nucleus with the help of specific
protein .HIF-1 protein with DNA binding activity. Functional HIF
transcription factors comprise 2 different subunits, that is, alpha
(α) and beta (β). The α subunit, of which there are 3 forms ( HIF-
1α, HIF-2α and HIF-3α) out of which HIF-1α and HIF-2α are
main, HIF-1α is oxygen sensitive, HIF-1α is expressed in almost
all cell types, and transcriptionally upregulates a large number of
genes, including those encoding Vascular endothelial growth
factor (VEGF), Glucose transporters, Glycolytic pathway enzymes
, Insulin-like growth factor-2, Endothelin-1, transferrin.

7. CONTD..
HIF-2  is the primary regulator of EPO production and also
plays an important role in enterocyte iron uptake.
HIF-β is continuously transcribed and its mRNA and protein are
maintained at constant levels irrespective of oxygen levels, the
availability of HIF-α is highly dependent on cellular oxygen
levels. Thus, the activity of the HIF transcription factor
heterodimer is relatively low under normal tissue oxygen
conditions called normaxia however, as cellular oxygen levels
decrease called hypoxia, HIF-α concentration increases, making
HIF progressively more functionally active.

8. STRUCTURE OF GENE
774/789 aa
HIF-1B/
ARNT bHLH A PAS B
826 aaHIF-1A bHLH A PAS B
TAD
C
ID
TAD
N
NLS-N NLS-C
Both bHLH and PAS are essential for dimerization and DNA-binding.
bHLH: basic helix-loop-helix domain;
PAS: domain with A and B repeats, amino-terminal (N) and
carboxyl-terminal (C) nuclear localization signal (NLS);
TAD: transactivation domain;

9. WHAT DOES HIF-1 DO?
1. Helps normal tissues as well as tumors to survive under
hypoxic conditions
2. HIF-1 is a transcription factor that turns on genes needed for
survival under hypoxic conditions.
3. So far, more than 40 target genes have been found to be
regulated by HIF-1.
4. These genes can be classified into 3 main groups:
HIF-1 5/2003 SFRBM Education Program Wang, Min 9

10. Some of main gene regulation by HIF-1

11. HIF-1 Target Genes
Erythropoeitin (EPO)
Nitric oxide synthase 2
(NOS2)
Transferrin
Transferrin receptor
Vascular endothelial
growth factor (VEGF)
VEGF receptor FLT-1
Group 1:
O2 Delivery
HIF-1 5/2003 SFRBM Education Program Wang, Min 11

12. Aldolase A
Aldolase C
Enolase 1 (ENO1)
Glucose transporter 1
Glyceraldehyde phosphate
dehydrogenase
Hexokinase 1
Hexokinase 2
Lactate dehydrogenase A
Phosphofructokinase L
Phosphoglycerate kinase 1
Pyruvate kinase M
Group 2:
Glucose
/Energy
Metabolism
HIF-1 5/2003 SFRBM Education Program Wang, Min 12

13. Insulin-like growth
factor 2 (IGF-2)
IGF binding protein 1
IGF binding protein 3
p21
p35srj
Group 3:
Cell Proliferation
/Viability
HIF-1 5/2003 SFRBM Education Program Wang, Min 13

14. Role of HIF-1 in

15. HOW BLOCKAGE OF HIF-1 OCCUR IN NORMAXIA
Ø Proline residue 402 & 564 in HIF-1 can be hydroxylated
by prolyl hydroxylase (PHD)
Ø The hydroxylation of proline causes the binding of von
Hippel-Lindau tumor suppressor (VHL).
Ø The binding of VHL leads to the ubiquitinylation of HIF-
1.
Ø Ubiquitinylation of HIF-1 results in degradation by
proteasome.

16. INHIBITION OF HIF-PH IN LOW O2 CONC.
Pro (402)
Pro (564)
HIF-alpha
OH
OH
G

β
 β
HRE Transcription
Low O2
Translocation
HIF-PH

17. PROLYL HYDROXYLASE IS O2-DEPENDENT
Ø The activation of prolyl hydroxylase depends on
several co-factors such as O2, Fe2+,
-ketoglutarate and ascorbate.
Ø Under hypoxia, prolyl hydroxylase cannot be
activated. Thus,
Ø HIF-1 accumulates and translocates
into nucleus. In the nucleus, it binds to HIF-1
forming HIF-1.
Ø HIF-1 binds to co-activators CBP/p300 and is
then activated.

19. Role of HIF-1 in

20. PATHWAY OF HIF-1

21. CONTD..
In hypoxia condition VHL, PHD, FIH molecules are
not activated so degradation of HIF-1(alpha) not
done because these molecules are O2 dependent
molecules.
1. VHL- von- Hippel Lindace protein
(Tumor supressor gene.)
2. FIH- Factor inhibiting HIF-1 (alpha)
(Hydroxylase at aspargin residue)
3. Ub- Ubiquintin

22. FACTOR INVOLVE IN INHIBITION & TRANSCRIPTION

23. BINDING SITES OF DEGRADING MOLECULES

25. ROLE OF HIF-1 IN CANCER CELL
In some analysis study of expression of gene in
cancer cell found that HIF-1 is over expressed in
these cell as compare with surrounding non-
cancer cell. Which leads to suppresses some
tumor suppression protein like p53.
Ø Tumor blood vessels are highly irregular and
disorganized.
Ø Most human solid tumors have pO2 values lower than
their normal tissues of origin.
Ø Severe hypoxia can rarely be found in normal tissues,
but these regions always exist in tumors.

26. DISEASES RELATED TO HIF-1
1. Anemia
2. Angiogenesis
3. Tumor
4. Glucose metabolism
5. CKD, chronic kidney disease
6. Ischemic cardiovascular disorders

27. HOW WE USE HIF-1 IN TREATMENT OF CANCER
1) By RNAi technique
2) By gene silencing
3) By producing drugs which hydroxylate HIF-1 alpha
subunit like PHD
4) By over expression of VHL, FIH molecules
5) By inhibing p300/CBT complex

28. DRUGS

29. REFERENCES
Ø GREGG L. SEMENZA* AND GUANG L. WANG
MoLECULAR AND CELLULAR BIoLoGY, Dec. 1992, p. 5447-5454 Vol. 12, No. 12 Copyright
© 1992, American Society for Microbiology
Ø MICHAEL S. GREENFIELD, STANFORD LAW REVIEW
VOL. 44 NO. 5 MAY 1992 PAGE NO.1051-1094
Ø Agani F., Semenza G.L.
(1998) Mersalyl is a novel inducer of vascular endothelial growth factor gene expression and
hypoxia-inducible factor 1 activity. Mol. Pharmacol. 54:749–754
Ø Genes Dev. 2000 Aug 15;14(16):1983-91.
Ø EPO erythropoietin [ Homo sapiens (human) ], Gene ID: 2056, updated on 2-Nov-2019
Ø Patrick H. Maxwell*, Michael S. Wiesener*, Gin-Wen Chang*, Steven C. Clifford†,
Emma C. Vaux‡, Matthew E. Cockman‡, Charles C. Wykoff‡, Christopher W. Pugh‡,
Eamonn R. Maher† & Peter J. Ratcliffe*‡
Ø Yale J Biol Med 2007 June; 80(2):51-60