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The Replisome

The Replisome

DNA replication is carried out by a large complex of proteins that act in a coordinated matter to achieve high-fidelity DNA replication. Together this complex is known as the DNA replication machinery or the replisome.
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...

The Replisome

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DNA replication is carried out by a large complex of proteins that act in a coordinated matter to achieve high-fidelity DNA replication. Together this complex is known as the DNA replication machinery or the replisome.
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Related Experiment Video

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Using Modified Synthetic Oligonucleotides to Assay Nucleic Acid-Metabolizing Enzymes

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DNA ligase I, the replicative DNA ligase.

Timothy R L Howes¹, Alan E Tomkinson

¹Biomedical Sciences Graduate Program, University of New Mexico, Cancer Research Facility MSC08 4640, 1 University of New Mexico, Albuquerque, NM, 87131-0001, USA, howes.timothy@gmail.com.

Sub-Cellular Biochemistry

|August 25, 2012

Summary

DNA ligase I enzymes join Okazaki fragments during DNA replication. Their N-terminal region interacts with PCNA, forming a double-ring structure crucial for efficient DNA repair and replication.

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Area of Science:

Molecular Biology
Biochemistry
Genetics

Background:

DNA replication requires joining Okazaki fragments on the lagging strand.
Eukaryotic DNA ligase I enzymes are key players in this process.
These enzymes possess a catalytic C-terminal region and a non-catalytic N-terminal region.

Purpose of the Study:

To elucidate the structural and functional roles of DNA ligase I in Okazaki fragment ligation.
To investigate the interaction between DNA ligase I and Proliferating Cell Nuclear Antigen (PCNA).
To understand the significance of the N-terminal region of DNA ligase I in DNA replication.

Main Methods:

Structural analysis of DNA ligase I domains.
Investigation of protein-protein interactions using biochemical assays.
Functional studies in DNA replication models.

Main Results:

DNA ligase I's C-terminal domains form a ring structure upon DNA nick binding.
The N-terminal region of DNA ligase I, containing a PCNA interaction motif, is essential for replication focus localization.
A double-ring structure model involving DNA ligase I and PCNA is proposed for Okazaki fragment joining.
Interactions with Replication Factor C are regulated by N-terminal phosphorylation.

Conclusions:

DNA ligase I's N-terminal region is critical for its recruitment and function at replication sites.
The proposed double-ring interaction facilitates efficient Okazaki fragment ligation.
Phosphorylation-regulated interactions with Replication Factor C are vital for DNA replication fidelity.