p8/TTDA Overexpression Enhances UV-Irradiation Resistance and Suppresses TFIIH Mutations in a Drosophila Trichothiodystrophy Model

Abstract

Mutations in certain subunits of the DNA repair/transcription factor complex TFIIH are linked to the human syndromes xeroderma pigmentosum (XP), Cockayne's syndrome (CS), and trichothiodystrophy (TTD). One of these subunits, p8/TTDA, interacts with p52 and XPD and is important in maintaining TFIIH stability. Drosophila mutants in the p52 (Dmp52) subunit exhibit phenotypic defects similar to those observed in TTD patients with defects in p8/TTDA and XPD, including reduced levels of TFIIH. Here, we demonstrate that several Dmp52 phenotypes, including lethality, developmental defects, and sterility, can be suppressed by p8/TTDA overexpression. TFIIH levels were also recovered in rescued flies. In addition, p8/TTDA overexpression suppressed a lethal allele of the Drosophila XPB homolog. Furthermore, transgenic flies overexpressing p8/TTDA were more resistant to UV irradiation than were wild-type flies, apparently because of enhanced efficiency of cyclobutane-pyrimidine-dimers and 6–4 pyrimidine-pyrimidone photoproducts repair. This study is the first using an intact higher-animal model to show that one subunit mutant can trans-complement another subunit in a multi-subunit complex linked to human diseases.

Drosophila p53 Is Required to Increase the Levels of the dKDM4B Demethylase after UV-induced DNA Damage to Demethylate Histone H3 Lysine 9

“…3E). We previously observed that the kinetics of CPD removal in third instar larvae can be detected 4 h after irradiation and occurs faster than in mammalian cells (32). Interestingly, the H3K9me3 demethylated state is maintained in heterochromatin for several hours until the H3K9me3 levels rise again (supplemental Fig.…”

Nucleotide Excision Repair and Transcriptional Regulation: TFIIH and Beyond

“…Interaction between p52 and p8/TTDA further strengthens the anchoring of TFIIH to DNA after a genotoxic attack (107). Interestingly, overexpression of p8/TTDA in p52-deficient Drosophila cells exhibiting a TTD phenotype or in human XPD-deficient cells abrogates their strong UV-sensitive phenotypes (108).…”

Physical and Functional Interactions between Drosophila Homologue of Swc6/p18Hamlet Subunit of the SWR1/SRCAP Chromatin-remodeling Complex with the DNA Repair/Transcription Factor TFIIH

“…In addition, overexpression of Dmp8 generates flies that are more resistant to UV irradiation (12). In this study, we report that the Dmp8 gene is encoded in a bicistronic transcript along with the fly homolog of the Swc6/p18…”

“…4B) suggests that the phenotypes observed in these flies are primarily due to the absence of Dmp8. To confirm this, we constructed transgenic flies that expressed either Dmp8 fused to a six-histidine tag (12) or Dmp18 containing the Myc epitope (see "Experimental Procedures"). These flies were crossed with the l(2)SH1279 flies to generate organisms that were homozygous for the l(2)SH1279 insertion with one or two copies of the transgene.…”

“…We have previously reported that in Drosophila, the overexpression of the p8 homolog (Dmp8) suppresses the phenotypes generated by mutations in other components of TFIIH, such as p52 (named Dmp52 in the fly) and XPB (named haywire in the fly) (11,12). In addition, overexpression of Dmp8 generates flies that are more resistant to UV irradiation (12).…”