Cell cycle-dependent TICRR/TRESLIN and MTBP chromatin binding mechanisms and patterns

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• DNA replication origin selection is crucial in eukaryotes but poorly understood in humans.
• Minichromosome maintenance (MCM) complexes are recruited to potential origins during G1.
• Yeast uses SLD3-SLD7 factors for MCM selection, but human mechanisms remain unclear.

Purpose of the Study:

• To investigate the binding mechanisms of human replication initiation factors TRESLIN (Sld3 ortholog) and MTBP (Sld7 ortholog).
• To determine the role of TRESLIN and MTBP in DNA replication initiation during G1 and S phases.
• To compare human origin selection mechanisms with those in yeast.

Main Methods:

• Examined genomic binding locations of TRESLIN and MTBP in G1-synchronized and asynchronously cycling human cells.
• Assessed TRESLIN and MTBP binding patterns in early S phase populations.
• Investigated the dependency of MTBP binding on TRESLIN and the requirement for licensed origins.

Main Results:

• TRESLIN and MTBP binding signals were higher in G1-synchronized cells compared to asynchronous cells.
• MTBP associated with early-mid replicating regions during S phase and showed G1-specific, TRESLIN-dependent chromatin association.
• TRESLIN and MTBP binding in G1 did not require pre-loaded MCM complexes at licensed origins.

Conclusions:

• A novel G1 chromatin binding mechanism for TRESLIN-MTBP was identified, independent of licensed origins.
• Distinct binding modes for MTBP in G1 and S phases suggest differential functions.
• Human DNA replication initiation factor binding diverges from yeast, indicating unique origin selection strategies.