In vivo structure-mediated regulation of ribonucleotide reductase in S. pombe

Schreurs, Ann-Sofie (2012) In vivo structure-mediated regulation of ribonucleotide reductase in S. pombe. Doctoral thesis (PhD), University of Sussex.

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Abstract

Sufficient and balanced pools of deoxyribonucleotide triphophates (dNTPs) is
crucial for high-fidelity DNA replication as well as correct DNA repair. The enzyme
RiboNucleotide Reductase (RNR) catalyses NDP to dNDP and is therefore an
essential enzyme by providing the “building blocks” to the cells. dNTPs production
needs to be tightly regulated in order to minimize mutation frequencies and prevent
genome instability.

RNR in S. pombe is composed of two proteins, Cdc22R1 and Suc22R2, and has
been described as a heterotetramer with a dimer of each subunit: the big subunit
Cdc22R1 and the small subunit Suc22R2. S. pombe also posseses an RNR inhibitor:
Spd1, as well as a second RNR regulator Spd2 which has been newly discovered.
Spd1 has been demonstrated to inhibit RNR and to regulate its activity throughout the
cell cycle. The detailed mechanism of the RNR regulation during the cell cycle or after
DNA damage is not entirely clear, as are the means of inhibition by Spd1. In order to
shed some light on the RNR complex and its regulation, we used various microscopybased
methods to study RNR in vivo as well as in vitro.

The data of this thesis suggest there are different forms of active RNR
heterocomplexes, found throughout the cell cycle in the cytoplasm as well as in the
nucleus. We propose that the precise stoichiometry of subunits in the complexes may
vary, or that the complex conformation may be modified in an Spd1-dependent
manner. In addition, treatment of the cells with a UV mimetic agent, 4NQO, seems to
promote RNR regulation in an Spd1-dependent manner. On the contrary, inhibition of
RNR by HydroxyUrea (HU) affects the RNR in a possible structure-related manner,
independently of Spd1 or Spd2. The in vivo observations correlate with structural
and/or oligomerization modifications of the RNR, representing a novel RNR regulation
in S. pombe.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Life Sciences > Biochemistry
Subjects: Q Science > QD Chemistry > QD0241 Organic chemistry > QD0415 Biochemistry
Q Science > QP Physiology > QP0501 Animal biochemistry > QP0603.R52 Ribonucleoside diphosphate reductase
Depositing User: Library Cataloguing
Date Deposited: 28 Jan 2013 09:52
Last Modified: 08 Sep 2015 14:17
URI: http://sro.sussex.ac.uk/id/eprint/43403

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