Hereditary mutations in the DNA helicases XPB and XPD lead to human diseases with different phenotypes reflecting increased cancers or increased cell death: xeroderma pigmentosum (XP), XP- linked Cockayne syndrome (CS), and trichothiodystrophy (TTD). These diseases reflect the disruption of different cellular pathways: Defective nucleotide-excision repair (NER) results in XP, perturbed transcription-coupled repair (TCR) leads to CS, and transcription abnormalities combined with defective NER cause TTD. In humans, XPB and XPD helicases are part of the ten subunit TFIIH transcription/repair complex, but disease-causing mutations cluster in XPB and particularly XPD rather than in the other TFIIH proteins, excepting TFB5, so these XP helicases appear key to controlling coordination of transcription and repair. Furthermore, the repair proteins XPG and CSB interact with the XP helicases in TCR. However, there is little knowledge at the molecular level about XPB and XPD, their helicase and repair activities, or their interactions with TFB5, CSB and XPG.
We aim to understand the molecular features underlying the specificity, activity, conformational controls and pathway coordination by the XPB and XPD helicases. Our hypothesis is that well-defined architectures, conformational states, and molecular interfaces of XPB and XPD helicases provide critical controls for transcription, NER, and TCR. We furthermore propose that characterizations of these features and their disruption by disease-causing mutations will provide a molecular basis to directly connect the inherited gene mutations to disease phenotypes. To test this, we herein propose to integrate structural and biophysical experiments (Tainer laboratory) with biochemical and biological experiments (Cooper laboratory). Our experiments on XPB and XPD domains and full-length proteins, their archaeal homologues, and their key assemblies will establish molecular architectures, conformational switching mechanisms, and allosteric interactions. We expect to characterize a prototypical set of helicase structures, their complexes with DNA and with protein partners, and to define the key interactions for their activities. The anticipated outcome of the proposed cross-disciplinary experiments is a molecular picture of the protein-DNA complexes, protein-protein interactions and functional states that orchestrate transcription and repair events mediated by XPB and XPD as components of TFIIH. These results will help provide a detailed molecular understanding of the processes that underlie the cancer and cell death disease phenotypes associated with XPB, XPD, TFB5, CSB and XPG patient mutations. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
1R01CA112093-01A2
Application #
7096103
Study Section
Radiation Therapeutics and Biology Study Section (RTB)
Program Officer
Knowlton, John R
Project Start
2006-04-01
Project End
2011-03-31
Budget Start
2006-04-01
Budget End
2007-03-31
Support Year
1
Fiscal Year
2006
Total Cost
$307,265
Indirect Cost
Name
Lawrence Berkeley National Laboratory
Department
Biophysics
Type
Organized Research Units
DUNS #
078576738
City
Berkeley
State
CA
Country
United States
Zip Code
94720
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Shin, David S; Pratt, Ashley J; Tainer, John A (2014) Archaeal genome guardians give insights into eukaryotic DNA replication and damage response proteins. Archaea 2014:206735
Sontz, Pamela A; Mui, Timothy P; Fuss, Jill O et al. (2012) DNA charge transport as a first step in coordinating the detection of lesions by repair proteins. Proc Natl Acad Sci U S A 109:1856-61
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