Ixr1p regulates oxygen-dependent HEM13 transcription

Area of Science:

• Molecular Biology
• Yeast Genetics
• Biochemistry

Background:

• HEM13 encodes coproporphyrinogen III oxidase, the rate-limiting enzyme in heme biosynthesis.
• HEM13 is a hypoxia-regulated gene repressed by Rox1p and Mot3p under aerobic conditions.

Purpose of the Study:

• Investigate the functional promoter regions of HEM13 during hypoxia.
• Determine the effect of deleting transcriptional regulators (Sut1p, Sut2p, Upc2p, Ecm22p, Ixr1p) on HEM13 expression.

Main Methods:

• Deletion analysis of transcriptional regulators.
• In vivo and in vitro DNA-binding assays of Ixr1p to the HEM13 promoter.
• Analysis of promoter regions crucial for hypoxic gene expression.

Main Results:

• Ixr1p is necessary for high HEM13 expression under hypoxic conditions.
• Ixr1p binds in vivo to the -577 to -419 region of the HEM13 promoter.
• Ixr1p binds in vitro to two specific DNA sequences within the promoter, with a consensus sequence KTTSAAYKGTTYASA being important for binding.

Conclusions:

• HEM13 expression regulation involves two high mobility group (HMG) domain proteins: Rox1p and Ixr1p.
• Ixr1p's interaction with the HEM13 promoter is crucial for hypoxic regulation.
• Protein-DNA interactions at the HEM13 promoter may differ between aerobic and hypoxic conditions.