Developmentally regulated usage of Physarum DNA replication origins.

Area of Science:

• Molecular Biology
• Cell Biology
• Developmental Biology

Background:

• Eukaryotic DNA replication origin usage is crucial for cell proliferation.
• Developmental regulation of replication origins in transcriptionally active cells remains largely unexplored.
• Physarum polycephalum offers a model system to study cell differentiation and its impact on genome replication.

Purpose of the Study:

• To investigate the developmental regulation of eukaryotic replication origins.
• To compare replication origin usage in different cell types of Physarum polycephalum.
• To determine the link between transcriptional activity and replication origin selection.

Main Methods:

• Two-dimensional agarose-gel electrophoresis to analyze replication intermediates.
• Comparison of origin usage in amoebae and plasmodia of Physarum polycephalum.
• Analysis of gene expression and replication patterns for specific loci.

Main Results:

• Constitutively transcribed genes (ribosomal RNA, actin) showed similar replication origin usage in both cell types.
• Cell-type-specific replication patterns were observed for profilin A (proA) and profilin P (proP) genes.
• proA replication shifted from promoter-proximal in amoebae to passive in plasmodia, correlating with expression changes.
• proP replication shifted from passive in amoebae to origin-associated in plasmodia, correlating with expression changes.

Conclusions:

• S phase reprogramming is linked to transcriptional reprogramming during Physarum cell differentiation.
• Replication origins can be either constitutively active or developmentally regulated.
• Replication origin usage, similar to gene regulation, is likely under epigenetic control during cellular differentiation.