GENE REGULATORY MECHANISMS
Research Focus
The bHLH/PAS (basic Helix-Loop-Helix/Per-Arnt-Sim homology) protein family
comprise a broad set of transcription factors with diverse roles in development
and homeostasis. The bHLH domain is a well known dimerisation and DNA binding
domain prevalent in developmental transcription factors. PAS domains are found
in proteins which sense and transmit signals relating to environmental or metabolic
status (eg PAS domains have been found to detect oxygen status, light, environmental
pollutants and redox or nutrient status). Our laboratory studies mechanisms
of signal transduction and gene regulation by several members of this family.
1. Mechanism and function of Nxf
The Nxf protein is a brain specific member of the bHLH/PAS family that was found
by the Koblar group to undergo a rapid increase in expression following chemically
induced epileptic seizure in rats. We have found that the Nxf protein can function
as a strong transcription activator, although this varies markedly in different
cell lines and is totally dependent on the co-expression of either the Arnt1
or Arnt2 partner protein. In collaboration with the Koblar group, we are currently
investigating the roles of Nxf in brain development and stress response.
2. Gene regulation by the Single Minded transcription
Factors
Single Minded 1 and 2 (Sim1 & 2) are encoded by separate genes and expressed
predominantly in the brain, muscle and kidney. Sim1 null mice do not survive
birth due to hypocellularity of neuroendocrine lineages in the hypothalamic-pituitary
axis, indicating a critical role for Sim1 in terminal differentiation of certain
peptide hormone secreting neurons. Sim1 deficiency has also been linked to early
onset obesity. Sim2 null mice die at birth due to a poorly characterised breathing
defect. We are currently deciphering target genes for each of the Sim proteins
and investigating signalling mechanisms which may regulate their function.
3. Deciphering the posttranslational code of the Dioxin
Receptor
The Dioxin Receptor (DR) is activated by environmental pollutants and notorious
for mediating the severe toxicity associated with dioxin and PCB poisoning.
DR null mice survive, but have impaired liver function due to incomplete vascularisation
and exhibit poor fertility. We are mapping a complete profile of posttranslational
modifications in the DR during its multi-step activation process and attempting
to link these to functions of early development and toxin metabolism.
4. Novel functions of the Hypoxia Inducible Factor
HIF-1a
HIF-1a is well established as a key transcription factor for inducing genes
involved in angiogenesis, erythropoiesis and enhanced glycolysis during hypoxic
stress. Somewhat surprisingly, HIF-1a is also found to induce some pro-apoptotic
genes and in certain circumstances can function as a transcription repressor.
We are investigating the mechanisms of these lesser known functions of HIF-1a
and relating these to new biological roles.
Recent publications
Collaborators & Linkages
Recent Publications
Furness, SB, Lees, MJ, Whitelaw, ML. (2007) The Dioxin (Aryl hydrocarbon) Receptor
as a model for adaptive responses of bHLH/PAS transcription factors. FEBS Letters,
581, 3616-25
Dave, KA, Hamilton, BR, Wallis, TP, Furness, SGB, Whitelaw ML, Gorman, JJ. (2007)
Identification of N,Ne-dimethyl-lysine in the murine dioxin receptor using MALD-TOF/TOF
and ESI-LTQ-Orbitrap-FT-MS. Int. J. Mass Spec., in press
Chapman-Smith, A. and Whitelaw, M.L. (2006) Novel DNA binding by a basic helix-loop-helix
protein: The role of the dioxin receptor pas domain. J. Biol. Chem. 281, 12535-45
Cameron P. Bracken, C.P., Fedele, A.O., Linke, S., Balrak, W., Lisy, K., Whitelaw,
M.L. and Peet, D.J. (2006) Cell-specific regulation of HIF-1alpha and HIF-2alpha
: Stabilisation and transactivation in a graded oxygen environment. J. Biol.
Chem. 281, 22575-85
Bracken, C.P., Whitelaw, M.L., Peet, D.J. (2005) Activity of hypoxia-inducible
factor 2a is regulated by association with the NF- K B essential modulator.
The Journal of Biological Chemistry 280: 14240-51
Kewley, R.J., Whitelaw, M.L. (2005) Phosphorylation inhibits DNA-binding of
alternatively spliced aryl hydrocarbon receptor nuclear translocator. Biochemical
and Biophysical Research Communications 338: 660-7
Chapman-Smith, A., Lutwyche, J.K., Whitelaw, M.L. (2004) Contribution of the
Per/Arnt/Sim (PAS) domains to DNA binding by the basic helix-loop-helix PAS
transcriptional regulators. The Journal of Biological Chemistry 279: 5353-62
Kewley, R.J., Whitelaw, M.L., Chapman-Smith, A. (2004) The mammalian basic
helix-loop-helix/PAS family of transcriptional regulators. The International
Journal of Biochemistry and Cell Biology 36: 189-204
Linke, S., Stojkoski, c., Kewley, R.J., Booker, G.W., Whitelaw, M.L., Peet,
D.J. (2004) Substrate requirements of the oxygen-sensing asparaginyl hydroxylase
factor-inhibiting hypoxia-inducible factor. The Journal of Biological Chemistry
279: 14391-7
Peet, D.J., Lando, D., Whelan, D.A., Whitelaw, M.L., Gorman, J.J. (2004) Oxygen-dependent
asparagine hydroxylation. Methods in Enzymology 381: 467-87
Bracken, C.P, Whitelaw, M.L., Peet, D.J. (2003) The hypoxia-inducible factors:
key transcriptional regulators of hypoxic responses. Cellular and Molecular
Life Sciences 60: 1376-93
Lando, D., Gorman, J.J., Whitelaw, M.L., Peet, D.J. (2003) Oxygen-dependent
regulation of hypoxia-inducible factors by prolyl and asparaginyl hydroxylation.
European Journal of Biochemistry 270: 781-90
Lees, M.J., Peet, D.J., Whitelaw M.L. (2003) Defining the role for XAP2 in stabilization
of the dioxin receptor. The Journal of Biological Chemistry 278: 35878-88
Anderson, P., McGuire, J., Rubio, C., Gradin, K., Whitelaw, M.L., Petterson,
S., Hanburg, A., Poellinger, L. (2002) A constitutively active dioxin/aryl hydrocarbon
receptor induces stomach tumours. Proceedings of the National Academy of Sciences
USA , 99: 9990-5
Fedele, A.O., Whitelaw, M.L., Peet, D.P. Regulation of gene expression by the
hypoxia inducible factors. Molecular Interventions 2:230-43
Lando, D., Peet, D. J., Gorman, J. J., Whelan, D. A., Whitelaw, M. L*., Bruick,
R. K*. (2002) FIH is an asparaginyl hydroxylase enzyme that regulates the transcriptional
activity of Hypoxia Inducible Factor. Genes and Development, 16, 1466-71. (*joint
senior author)
Lando, D., Peet, D.J., Pongratz, I., Whitelaw, M.L. (2002) Mammalian Two-Hybrid
Assay Showing Redox Control of HIF-Like Factor. Methods in Enzymology , Vol.
353
Lando, D., Peet, D.J., Whelan, D.A., Gorman, J.J., Whitelaw, M.L. (2002) Asparagine
Hydroxylation of the HIF Transactivation Domain: A hypoxic Switch. Science 295:858-61
Lees, M.J., Whitelaw, M.L. (2002) Mediation of dioxin receptor transcription
by Ara9(XAP/AIP) Toxicology 181-182:143-6
Swanson, H.I., Whitelaw, M.L., Petrulis, J.R. and Perdew, G.H. (2002) Use
of [1251]4'-Iodoflavone as a tool to characterize ligand dependant differences
I Ah receptor behaviour. Journal of biochemical and molecular toxicology 16:
298-310
Woods, S., Whitelaw, M.L. (2002) Differential activities of murine SIM1and
SIM2 on a hypoxic response element: Crosstalk between bHLH/PAS transcription
factors. The Journal of Biological Chemistry 277:10236-43
McGuire, J., Okamoto, K., Whitelaw, M.L., Tanaka, H., Poellinger, L. (2001)
Definition of a Dioxin Receptor Mutant that is a Constitutive Activator of Transcription.
Journal of Biological Chemistry, 276, 41841-41849
Lando, D., Pongratz, I., Poellinger, L., Whitelaw, M.L. (2000) A Redox Mechanism
Controls Differential DNA Binding Activities of the Hypoxia Inducible Factors
HIF-1a and HIF-Like-Factor, Journal of Biological Chemistry, 275, 4618-4628
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