DNA-Protein Cross-links: Formation in Cells and Tissues …

 

 

DNA-Protein Cross-links: Formation in Cells and

Tissues, Repair, and Inhibition of DNA Transcription

SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE

UNIVERSITY OF MINNESOTA

A THESIS

BY

Daeyoon Park

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS

FOR THE DEGREE OF

MASTER OF SCIENCE

Dr. Natalia Y. Tretyakova, Advisor

April 2019

ⓒ Daeyoon Park, 2019

Acknowledgement

First and foremost, I would like to thank my advisor, Dr. Natalia Tretyakova, for her

great support and guidance throughout my degree. She was a great role model for me as a

scientist, and all the opportunities in her lab encouraged me to grow as a scientist. I feel

very fortunate to have worked with such a great mentor who inspires her students.

I thank Dr. Colin Campbell for his advice and supports during my graduate career. I also

want to acknowledge him for the collaboration throughout my projects and valuable

feedback he has provided on my work. I would like to express my thanks to my thesis

committee chair, Dr. Kate Adamala, and members for their advice, support, and

feedbacks throughout my thesis.

I wish to thank Dr. Mark Greenberg and Dr. Kun Yang at John Hopkins University for

the opportunities, allowing me to contribute to their project focused on DNA-protein

cross-links induced by monofunctional alkylating agents. Furthermore, I would like to

thank all the collaborators who contributed to my projects, especially Dr. Lei Li (The

University of Texas MD Anderson Cancer Center), Dr. Yuichi Machida (Mayo Clinic), Dr.

Deborah Ferrington (University of Minnesota), and Dr. Ashis Basu (University of

Connecticut).

I would like to thank to the former and current lab members in the Tretyakova lab who

helped me with my projects and provided great friendship and valuable discussions.

I wish to thank my parents, Jindal Park and Youngsun Lee, for making me see the greater

picture, and my sister, Jeeyoon, for encouraging me. And lastly, I would like to thank my

wife, Hyojin, for her perpetual love and support.

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Abstract

DNA is constantly damaged by exogenous and endogenous agents, generating a range of

nucleobase lesions. It is important to understand the biological consequences and repair

mechanisms of DNA adducts. Cellular proteins can become covalently trapped on DNA

to generate DNA-protein crosslinks (DPCs). Because of their unusually bulky nature,

DPCs are anticipated to block many cellular processes including replication,

transcription, and repair. However, cellular effects of DPCs have not been fully

elucidated. Chapter 1 of this thesis provides background information on the formation,

biological consequences, and repair pathways of DPCs studied in previous studies.

In Chapter 2, we employed a quantitative nanoLC-ESI+-MS/MS assay to investigate the

formation of free radical-induced DPCs between thymidine in DNA and tyrosine

sidechains of proteins. This methodology was used to examine the role of SPRTN

protease and immunoproteasome in DPC repair in human cells and mouse models.

In Chapter 3, a mass spectrometry based CTAB assay was used to study the effects of

DNA-peptide crosslinks on transcription in human cells. We constructed plasmid

molecules containing DPCs between C5 of dC and lysine sidechains of polypeptides in

order to mimic conjugates that form endogenously at DNA epigenetic marks (5-formylc-

dC). Lesion bearing and control plasmids were transfected into human cells, and the

amounts of RNA transcripts were determined using a mass spectrometry based approach.

Moreover, DNA lesion bearing plasmid models were used to determine the importance of

NER pathway in DPC repair. In Chapter 4, we investigated in vivo formation of DPCs in

cells exposed to monofunctional alkylating agent, methyl methanesulfonate (MMS). A

mass spectrometry-based TMT proteomics approach was used to characterize MMS-

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induced DNA-protein cross-linking in Chinese hamster lung fibroblasts (V79). utilizing

Our results revealed that DPCs can be produced via nucleophilic attack of proteins at the

C8 position of N7-methylguanine (MdG). Our results revealed novel DPC formation

mechanisms and the toxicities of monofunctional agent induced DPCs.

In summary, mass spectrometry-based quantification was used to the amounts of free

radical induced DPCs in cells, providing evidence for the role of DPC proteolysis in

repair, while CTAB assay demonstrated the effect of endogenously formed DPCs on

transcription. Moreover, a mass spectrometry-based methodology was applied to examine

a novel DPC formation mechanism following treatment with monofunctional alkylating

agents.

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TABLE OF CONTENTS

ACKNOWLEDGEMENTS……….………………………….………………………….. i

ABSTRACT……………………………….……………………….………….………….. ii

LIST OF TABLES …………………………..……………………………….………… viii

LIST OF SCHEMES.………………………..…………………….…………………… ix

LIST OF FIGURES.…………………….………………………………………..……. xii

LIST OF ABBREVIATIONS.…………………….…………………………………. xvi

1. Introduction……………………………………………………………………….….. 1

1.1. DNA Damage and Its Biological Influence…………………………………. 1

1.2. DNA-Protein Crosslinks……………………………………………………… 3

1.2.1. Types of DPC Formation in Cells…………………………………. 6

1.2.2. DPC Formation in Cells……………………………………….…… 6

1.3. DPC-inducing Agents Studied in This Thesis………………………………. 9

1.3.1. Reactive Oxygen Species (ROS)………………………………….. 9

1.3.1.1. Endogenous Formation of Reactive Oxygen Species …. 13

1.3.1.2. Exogenous Formation of Reactive Oxygen Species …… 14

1.3.1.3. ROS induced DNA Protein Crosslinks………………… 14

1.3.2. Ionizing Radiation………………………………………………… 17

1.3.3. Methyl Methanesulfonate (MMS)………………………….……. 17

1.3.4. 5-Formylcytosine Epigenetic Marks……………………………… 20

1.4. DPC repair pathways…………………………………………….………. 23

1.4.1. Significance of DNA Protein Crosslink Repair………………….. 23

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1.4.2. DPC Repair by Canonical Repair Pathways……………………… 23

1.4.3. Endogenous DNA Damage by Attempted DNA Repair…………. 27

1.4.4. Novel DPC-Proteolysis Repair ………………………………….. 29

1.4.4.1. Spartan DPC Protease in DPC Repair…………………. 29

1.4.4.2. Proteasome in DPC Repair…………………………….. 32

1.4.4.3. Mechanism of Novel DPC Repair Pathway……………. 33

2. Role of Proteolysis in Repair of Free Radical-induced DNA-Protein Crosslinks in

Mouse Cells and Tissues………………………….……………………………………. 35

2.1. Introduction……………………………….……………………………….. 36

2.2. Materials and Methods……………………………………………….…… 40

2.3. Results……………………………………….………………………..…… 46

2.3.1. Cytotoxicity and Quantification of DPCs in the IR treated WT and

SPRTN deficient cells…………………………………………………… 46

2.3.2. Quantitation of DPCs in Wild Type and SPRTN Deficient Mouse

Tissues…………………………………………………………………… 52

2.3.3. Method Development for Isotope Dilution Tandem Mass

Spectrometry Assay…………………………………………………….. 55

2.3.4. Quantitation of DPCs in IR treated Mouse Brain and Liver

samples………………………………………………………………….. 58

2.3.5. Quantitation of DPCs In Tissue of Immunoproteasome Knockout

Mouse…………………………………………………………………… 60

2.4. Discussion………………………………………………………………….. 62

3. Effects of 5-Formylcytosine Mediated DNA-Peptide Cross-links on Transcription

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in Human Cells. ……………………………………………………………………….. 67

3.1. Introduction………………………………………………….……………. 68

3.2. Materials and Methods……………………………………………..………70

3.3. Results……….………………………………………………………………76

3.3.1. Generation of Plasmid Substrate Containing DPCs…………….…76

3.3.2. Influence of DNA-peptide and DNA-Lys Cross-links on

Transcription in Human Cells ………………………………………….. 82

3.3.3. Influence of NER on Transcription bypass of DpCs ……………. 87

3.3.4. Transcriptional Mutagenesis at Longer Timepoints……………… 89

3.4. Discussion……………………………………….………………………… 91

4. Quantification of Monofunctional Agent-induced DNA-Protein Crosslink in vivo

…………………………………………………………………………………………… 94

4.1. Introduction……………………….………………………………………. 95

4.2. Materials and Methods………….……………………………….……….. 99

4.3. Results…….………………………………………………………….…… 104

4.3.1. Concentration-dependent Formation of DPCs in MMS-treated

human cells……………………………………………………………. 104

4.3.2. Identification of MMS induced Cross-linked Proteins in HT1080

cells……………………………………………………………………. 107

4.3.3. Quantification of MMS induced Cross-linked Proteins in V79

cells……………………………………………………………………. 112

4.4. Discussion……….……………………..………………………………… 116

5. Summary and Conclusions………………….……………………………………… 118

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