Polypurine/polypyrimidine sequences as cis-acting transcriptional regulators

Area of Science:

• Molecular Biology
• Genetics
• Bioinformatics

Background:

• Repetitive DNA sequences, including polypurine/polypyrimidine [poly(Pu/Py)] sequences, are found near gene promoters and within transcribed regions.
• Evidence suggests these repetitive sequences may play a role in gene expression regulation.

Purpose of the Study:

• To investigate the influence of poly(Pu/Py) sequences on gene expression levels.
• To determine if poly(Pu/Py) sequences function as cis-acting transcriptional regulators.

Main Methods:

• Construction of prokaryotic and eukaryotic expression vectors with poly(Pu/Py) repeats within or upstream of the lacZ reporter gene.
• In vivo expression studies in mammalian cells and yeast.
• Analysis of yeast genomic sequences for the occurrence of poly(Pu/Py) sequences upstream of open reading frames (ORFs).

Main Results:

• Poly(Pu/Py) sequences within the reporter gene did not significantly inhibit expression in mammalian cells.
• Poly(Pu/Py) sequences upstream of the reporter gene caused a several-fold reduction in gene expression in mammalian cells.
• Similar down-regulation of gene expression was observed in yeast when poly(Pu/Py) sequences were integrated upstream of the reporter gene.
• Bioinformatic analysis revealed a high frequency of poly(Pu/Py) sequences upstream of yeast ORFs.

Conclusions:

• Poly(Pu/Py) sequences located upstream of genes can act as cis-acting transcriptional regulators.
• These sequences contribute to the down-regulation of gene expression in eukaryotic systems.
• The findings provide insights into the regulatory role of repetitive DNA elements in gene expression.