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Dna2 exhibits a unique strand end-dependent helicase function.

Lata Balakrishnan¹, Piotr Polaczek, Subhash Pokharel

¹Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.

The Journal of Biological Chemistry

|October 9, 2010

Summary

This summary is machine-generated.

Dna2 endonuclease/helicase requires threading onto unblocked 5' flaps to activate its helicase function during DNA replication. This end-loading mechanism ensures coordinated DNA processing and prevents excessive flap formation.

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Area of Science:

Molecular Biology
Biochemistry
Genetics

Background:

Dna2 endonuclease/helicase is crucial for eukaryotic DNA replication, specifically in processing Okazaki fragments.
It cleaves long DNA flaps, a process involving unique substrate binding and threading.
The enzyme's helicase activity is ATP-dependent and moves it along the DNA flap.

Purpose of the Study:

To investigate the mechanism of Dna2 helicase loading onto DNA substrates.
To determine if Dna2 can load internally or requires end-entry for helicase activity.
To understand how Dna2's loading mechanism relates to its nuclease function.

Main Methods:

Utilized two nuclease-dead Dna2 mutants.
Employed DNA substrates simulating Okazaki fragments with varying flap lengths.
Assessed helicase activity based on substrate threading and movement.

Main Results:

Dna2 requires threading onto an unblocked 5' flap to exhibit helicase activity.
This end-loading requirement persists even on very long single-stranded DNA regions.
Nuclease-dead Dna2 mutants demonstrated the necessity of flap end entry for helicase function.

Conclusions:

Dna2 is a eukaryotic helicase that must load from the DNA end, unlike typical internal loaders.
This unique loading mechanism likely ensures coordination between Dna2's helicase and nuclease activities.
The end-loading requirement prevents the formation of excessively long flaps during DNA transactions.