# Chemistry and Biology of DNA Ligation

> **NIH NIH R01** · UNIVERSITY OF MICHIGAN AT ANN ARBOR · 2021 · $50,490

## Abstract

Abstract of Current Award
The overall goal of this proposal is to determine the mechanism and specificity of human DNA
ligases. All organisms have an absolute requirement for DNA replication and DNA repair in
order to synthesize new cells and to maintain correct cellular functions. Given its central
importance, there is a great deal of interest in studying these pathways. DNA ligases are
essential for DNA replication and most DNA repair pathways, however there are many
fundamental questions about how DNA ligases function and our existing models lag far behind
those that are available for DNA polymerases. We believe that it is essential to learn the
molecular mechanism of human DNA ligases and that the insights gained from this endeavor
will have significant value to human health. Some examples of where this knowledge could be
useful is in patients that suffer deficiency in DNA ligase function and in abnormal states in which
ligases have been overexpressed such as cancer. We will use quantitative mechanistic
enzymology techniques to characterize human DNA ligase 1 (LIG1) and DNA ligase 3 (LIG3).
Genetic and cellular observations suggest that these enzymes share some redundant biological
functions, but that distinct functions exist for each gene product. We will extend our previous
kinetic and structural studies of LIG1 to understand specificity of this enzyme and to define the
minimal steps in locating and engaging a single strand break. This work will be supported by
additional crystal structures that will characterize the enzyme-bound intermediates that have not
been previously characterized. We have recently succeeded in producing large quantities of
recombinant LIG 3 alpha and beta isoforms and we will perform a kinetic and thermodynamic
characterization to understand similarities and differences with LIG1. For both enzymes, we will
use site-directed mutagenesis to target specific functions, such as metal binding, DNA binding,
and catalytic activity. Analysis of these mutant proteins will provide an understanding of the
molecular features of eukaryotic DNA ligation that will be invaluable to understand ligase
function in normal cells and in human disease

## Key facts

- **NIH application ID:** 10386077
- **Project number:** 3R01GM130763-03S1
- **Recipient organization:** UNIVERSITY OF MICHIGAN AT ANN ARBOR
- **Principal Investigator:** Patrick J O'Brien
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $50,490
- **Award type:** 3
- **Project period:** 2018-12-01 → 2022-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10386077

## Citation

> US National Institutes of Health, RePORTER application 10386077, Chemistry and Biology of DNA Ligation (3R01GM130763-03S1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10386077. Licensed CC0.

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