Multiple regulatory proteins mediate repression and activation by interaction with the yeast Mig1 binding site

Area of Science:

• Molecular Biology
• Yeast Genetics
• Transcriptional Regulation

Background:

• Mig1 is a key protein mediating glucose repression in yeast.
• Mig1 binds to GC-rich sequences upstream of glucose-repressible genes.
• The regulation of Mig1 sites is complex and not fully understood.

Purpose of the Study:

• To investigate the regulation of transcription mediated by an isolated Mig1 binding site.
• To identify factors involved in glucose repression and activation at Mig1 sites.
• To explore the role of Mig1 and other proteins in regulating gene expression.

Main Methods:

• Utilized reporter gene assays with UAS(CYC1) and UAS(ADH1).
• Introduced mutations in regulatory genes (snf1, reg1, cyc8, tup1) and MIG1/MIG2 genes.
• Performed band shift assays with yeast cell extracts.

Main Results:

• The Mig1 site mediated glucose repression, responsive to regulatory mutations.
• Deletion of MIG1 reduced repression; mig1 mig2 double mutant showed complete loss of repression.
• The Mig1 site activated transcription with UAS(ADH1), and mutations in SUC2 promoter binding sites abolished this activation.
• Band shift assays confirmed Mig1 as the primary in vitro binder to the Mig1 site, independent of glucose or specific mutations.

Conclusions:

• An unknown activator, distinct from known proteins like Mig1, Mig2, Msn2, or Msn4, binds to the Mig1 site.
• This activator plays a role in SUC2 gene expression and potentially other genes.
• While Mig1 is the main in vitro binder, its role in repression is modulated by other factors and potentially an unknown activator.