Biochemistry, Biophysics, and Structural Biology Commons^™

New Dna Repair And Demethylation Functions In Uracil Dna Glycosylase Superfamily, Chenyan Chang

All Dissertations

Uracil-DNA glycosylase (UDG) superfamily, which consists of several groups of enzymes that recognize the damaged DNA bases and initiate the base excision repair (BER) pathway, is most important in dealing with DNA deamination and other base modifications. Thymine DNA glycosylase (TDG), which belongs to family 2 in the UDG superfamily, is able to specifically recognize and cleave the 5-methylcytosine (mC) oxidative derivatives including 5-formylcytosine (fC), 5-carboxylcytosine (caC), 5-hydromethyluracil (hmU) caused by active demethylation or DNA damage. My dissertation work is mainly focused on the fC and caC glycosylase activity within UDG superfamily. Chapter 1 is a general introduction to the …

Dna Glycosylases Remove Oxidized Base Damages From G-Quadruplex Dna Structures, Jia Zhou

Graduate College Dissertations and Theses

The G-quadruplex DNA is a four-stranded DNA structure that is highly susceptible to oxidation due to its G-rich sequence and its structure. Oxidative DNA base damages can be mutagenic or lethal to cells if they are left unrepaired. The base excision repair (BER) pathway is the predominant pathway for repair of oxidized DNA bases. DNA glycosylases are the first enzymes in BER and are responsible for removing base lesions from DNA. How DNA glycosylases remove base lesions from duplex and single-stranded DNA has been intensively studied, while how they act on G-quadruplex DNA remains to be explored.

In Chapter II …

Specificity And Catalytic Mechanism Of Dna Glycosylases In Udg Superfamily, Bo Xia

All Dissertations

DNA can be damaged by several kinds of endogenous and exogenous reactive nitrogen species. Under nitosative stress, uracil (U), hypoxanthine (I), xanthine (X) and oxanine (O) are four major deaminated DNA bases derived from cytosine (C), adenine (A) and guanine (G) respectively. To repair this type of DNA damage, several different repair pathways are involved.

My dissertation work mainly focused on the uracil-DNA glycosylase (UDG) superfamily, which includes several groups of enzymes that recognize the damaged DNA bases and initiate the base excision repair (BER) pathway, one of the most important repair pathways to deal with deaminated DNA bases. Chapter …